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Tamilnadu Samacheer Kalvi 12th Chemistry Solutions Chapter 9 Electro Chemistry

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Samacheer Kalvi 12th Chemistry Chapter 9 Electro Chemistry Textual Evaluation Solved

Samacheer Kalvi 12th Chemistry Electro Chemistry Multiple Choice Questions
Question 1.
The number of electrons that have a total charge of 9650 coulombs is ………..
(a) 6.22 x 10²³
(b) 6.022 x 10²⁴
(c) 6.022 x 10²²
(d) 6.022 x 10^-34
Answer:
(c) 6.022 x 10²²
Hint: IF = 96500 C = 1 mole of e^– = 6.023 x 10²³ e^–
9650 C = \(\frac{6.22 \times 10^{23}}{96500} \times 9650\) = 6.022 x 10²²

Question 2.
Consider the following half cell reactions:
Mn²⁺ + 2e^– → Mn E° = – 1.18V
Mn²⁺ → Mn³⁺ + e^– E = – 1.51V
The E for the reaction 3Mn²⁺ → Mn+2Mn³⁺, and the possibility of the forward reaction are respectively.
(a) 2.69V and spontaneous
(b) – 2.69 and non spontaneous
(c) 0.33V and Spontaneous
(d) 4.18V and non spontaneous
Answer:
(b) – 2.69 and non spontaneous
Hint: Mn⁺ + 2e^– → Mn(E⁰_red) = 1.18V
2[Mn²⁺ → Mn³⁺ + e^–] (E⁰_ox) = – 1.51V
3Mn²⁺+ → Mn³⁺ + 2Mn³⁺ + (E⁰_cell) = ?
E⁰_red = (E⁰_ox) + (E⁰_cell)
= – 1.51 – 1.18 and non spontaneous
= – 2.69 V
Since E° is – ve ∆G is +ve and the given forward cell reaction is non – spontaneous.

Question 3.
The button cell used in watches function as follows
Zn_(s) + Ag₂O_(s) + H₂O₍₁₎ \(\rightleftharpoons\) 2Ag_(s) + Zn²⁺_(aq) + 2OH^–_(aq) the half cell potentials are
Ag₂O_(s) + H₂O₍₁₎ + 2e^– →2Ag_(S) + 2OH^–_(aq) E° = 034V. The cell potential will be
(a) 0.84V
(b) 1.34V
(c) 1.10V
(d) 0.42V
Answer:
(c) 1.10V
Hint: Anodic oxidation: (Reverse the given reaction)
(E⁰_ox ) = 0.76V cathodic reduction
E⁰_cell = (E⁰_ox) + (E⁰_red) = 0.76 + 0.34 = 1.1V

Question 4.
The molar conductivity of a 0.5 mol dm^-3 solution of AgNO₃ with electrolytic conductivity of 5.76 x 10^-3S cm^-1at 298 K is ………….
(a) 2.88 S cm² mo1^-1
(b) 11.52 S cm² mol^-1
(c) 0.086 S cm² mol^-1
(d) 28.8 S cm² mol^-1
Answer:
(b) 11.52 S cm² mol^-1
Hint:
A = \(\frac { k }{ M }\) x 10^-3 mol^-1 m³

= 11.52 S cm² mol^-1

Question 5.

Calculate A⁰_HOAC using appropriate molar conductances of the electrolytes listed above at infinite dilution in water at 25°C.
(a) 517.2
(b) 552.7
(c) 390.7
(d) 217.5
Answer:
(c) 390.7
Hint:

(426.2 + 91) – (126.5) = 390.7

Question 6.
Faradays constant is defined as
(a) charge carried by I electron
(b) charge carried by one mole of electrons
(c) charge required to deposit one mole of substance
(d) charge carried by 6.22 X 10¹⁰ electrons
Answer:
(b) charge carried by one mole of electrons
Hint:
IF = 96500 C = 1 charge of mole of e^– = charge of 6.022 x 10²³ e^–

Question 7.
How many faradays of electricity are required for the following reaction to occur
MnO^–₄ → Mn²⁺
(a) 5F
(b) 3F
(C) IF
(d) 7F
Answer:
(a) 5F
Hint:
7MnO^–₄ + 5e^– → Mn²⁺ + 4H₂O
5 moles of electrons i.e., 5F charge is required.

Question 8.
A current strength of 3.86 A was passed through molten Calcium oxide for 41 minutes and 40 seconds. The mass of Calcium in grams deposited at the cathode is (atomic mass of Ca is 40g / mol and IF = 96500C).
(a) 4
(b) 2
(c) 8
(d) 6
Answer:
(b) 2
Hint: m = ZIt
41mm 40sec = 2500 seconds
= \(\frac { 40 x 3.86 x 2500 }{ 2 x 96500 }\)
Z = \(\frac { m }{ n x 96500 }\) = \(\frac { 40 }{ 2 x 96500 }\)
= 2g

Question 9.
During electrolysis of molten sodium chloride, the time required to produce 0.1 mol of chlorine gas using a current of 3A is ………..
(a) 55 minutes
(b) 107.2 minutes
(c) 220 minutes
(d) 330 minutes
Answer:
(b) 107.2 minutes
Hint: \(\frac { m }{ ZI }\) (mass of 1 mole of Cl₂ gas = 71)
t = \(\frac { m }{ ZI }\) mass of 0.1 mole of Cl₂ gas = 7.1 g mol^-1)

Question 10.
The number of electrons delivered at the cathode during electrolysis by a current of 1 A in 60 seconds is (charge of electron = 1.6 x 10^-19C)
(a) 6.22 x 10²³
(b) 6.022 x 10²⁰
(c) 3.75 x 10²⁰
(d) 7.48 x 10²³
Answer:
(c) 3.75 x 10²⁰
Hint: Q = It
= 1A x 60S
96500 C charge 6.022 x 10²³ electrons
60 C charge = \(\frac{6.022 \times 10^{23}}{96500} \times 960\)
= 3.744 x 10²⁰ electrons

Question 11.
Which of the following electrolytic solution has the least specific conductance?
(a) 2N
(b) 0.002N
(c) 0.02N
(d) 0.2N
Answer:
(b) 0.002N
Hint: In general, specific conductance of an electrolyte decreases with dilution. SO, 0.002N solution has least specific conductance.

Question 12.
While charging lead storage battery
(a) PbSO₄ on cathode is reduced to Pb
(b) PbSO₄ on anode is oxidised to PbO₄
(c) PbSO₄ on anode is reduced to Pb
(d) PbSO₄ on cathode is oxidised to Pb
Answer:
(c) PbSO₄ on anode is reduced to Pb.
Hint: Charging: anode: PbSO₄(s) + 2e^– → Pb (s) + SO₄^-2 (aq)
Cathode: PbSO₄(s) + 2H₂O (1) → PbO₂ (s) + SO₄^-2 (aq) + 2e_–

Question 13.
Among the following cells
I. Leclanche cell
II. Nickel – Cadmium cell
III. Lead storage battery
IV. Mercury cell
Primary cells are …………
(a) I and IV
(b) I and III
(c) III and IV
(d) II and III
Answer:
(a) I and IV

Question 14.
Zinc can be coated on iron to produce galvanized iron but the reverse is not possible. It is because
(a) Zinc is lighter than iron
(b) Zinc has lower melting point than iron
(c) Zinc has lower negative electrode potential than iron
(d) Zinc has higher negative electrode potential than iron
Answer:
(d) Zinc has higher negative electrode potential than iron
Hint: E⁰_Zn⁺|Zn = – 0.76V and E⁰_Fe²⁺|Fe = 0.44V. Zinc has higher negative electrode potential than iron, iron cannot be coated on zinc.

Question 15.
Assertion: pure iron when heated in dry air is converted with a layer Of rust.
Reason: Rust has the composition Fe₃O₄
(a) If both assertion and reason are true and reason is the correct explanation of assertion.
(b) If both assertion and reason are true but reason is not the correct explanation of assertion.
(c) assertion is true but reason is false
(d) both assertion and reason are false.
Answer:
(d) both assertion and reason are false.
Hint: Both are false

1. Dry air has no reaction with iron
2. Rust has the composition Fe₂O₃ x H₂O

Question 16.
In H₂ – O₂ fuel cell the reaction occur at cathode is ……….
(a) O₂(g) + 2H₂O (l) + 4e^– → 4OH^–(aq)
(b) H⁺(aq) + OH^–(aq) → H₂O (l)
(c) 2H₂(g) + O₂(g) → 2H₂O (g)
(d) H⁺ + e^– → 1/2 H₂
Answer:
(a) O₂(g) + 2H₂O (l) + 4e^– → 4OH^–(aq)

Question 17.
The equivalent conductance of M/36 solution of a weak monobasic acid is 6mho cm² and at infinite dilution is 400 mho cm². The dissociation constant of this acid is ………….
(a) 1.25 x 10^-16
(b) 6.25 x 10 ^-6
(c) 1.25 x 10^-4
(d) 6.25 x 10^-5
Answer:
(b) 6.25 x 10 ^-6
Hint: α = \(\frac { 6 }{ 400 }\)
K_a = α²C = \(\frac { 6 }{ 400 }\) x \(\frac { 6 }{ 400 }\) x \(\frac { 1 }{ 36 }\)
= 6.25 x 10^-6

Question 18.
A conductivity cell has been calibrated with a 0.01M, 1:1 electrolytic solution (specific conductance (K = 1.25 x 10^-3 S cm^-1 ) in the cell and the measured resistance was 800Ω at 25⁰ C . The cell constant is,
(a) 10^-1 cm^-1
(b) 10^-1 cm^-1
(c) 1 cm^-1
(d) 5.7 x 10^-12
Answer:
(c) 1 cm^-1
Hint: R = p.\(\frac { 1 }{ A }\)
Cell constant = \(\frac { R }{ ρ }\) = k.R \((\frac { 1 }{ ρ } =k)\) = 1.25 x 10^-3 f^-1cm^-1 x 800Ω = 1cm^-1

Question 19.
Conductivity of a saturated solution of a sparingly soluble salt AB (1:1 electrolyte) at 298K is 1.85 x 10^-5 S m^-1. Solubility product of the saltAB at 298K (Λ⁰_m)_AB = 14 x 10^-3 S m² mol^-1.
(a) 5.7 x 10^-2
(b) 1.32 x 10¹²
(c) 7.5 x 10^-12
(d) 1.74 x 10^-12
Answer:
(d) 1.74 x 10^-12

Question 20.
In the electrochemical cell: Zn|ZnSO₄ (0.01M)||CuSO₄ (1.0M)|Cu , the emf of this Daniel cell is E₁. When the concentration of ZnSO₄ is changed to 1.0 M and that CuSO₄ changed to 0.0 1M, the emf changes to E₂. From the followings, which one is the relationship between E₁ and E₂?
(a) E₁ < E₂
(b) E₁ > E₂
(c) E₂ = 0↑E₁
(d) E₁ = E₂
Answer:
(b) E₁ > E₂
Hint:

Question 21.
Consider the change in oxidation state of Bromine corresponding to different emf values as shown in the diagram below:

Then the species undergoing disproportional is …………..
(a) Br₂
(b) BrO₄^–
(c) BrO₃^–
(d) HBrO
Answer:
(d) HBrO
Hint:

(E_cell)_A = – 1.82 + 1.5 = – 0.32V
(E_cell)_B = – 1.5 + 1.595 = + 0.095V
(E_cell)_C = 1.595 + 1.0652 = – 0.529V
The species undergoing disproportionation is HBrO

Question 22.
For the cell reaction
2Fe³⁺(aq) + ^2I(aq) → 2Fe²⁺ (aq) + I₂(aq)
EC⁰_cell = 0.24V at 298K. The standard Gibbs energy (∆, G⁰ ) of the cell reactions is …………
(a) – 46.32 KJ mol^-1
(b) – 23.16 KJ mol^-1
(c) 46.32 KJ mol^-1
(d) 23.16 KJ mor^-1
Answer:
(a) – 46.32 KJ mol^-1

Question 23.
A certain current liberated 0.504gm of hydrogen in 2 hours. How many grams of copper can be liberated by the same current flowing for the same time in a copper sulphate solution?
(a) 31.75
(b) 15.8
(c) 7.5
(d) 63.5
Answer:
(b) 15.8

Question 24.
A gas X at 1 atm is bubble through a solution containing a mixture of 1MY^– and 1MZ^-1 at 25°C . If the reduction potential of Z > Y> X, then
(a) Y will oxidize X and not Z
(b) Y will oxidize Z and not X
(c) Y will oxidize both X and Z
(d) Y will reduce both X and Z
Answer:
(a) Y will oxidize X and not Z

Question 25.
Cell equation: A²⁺ + 2B^– → A²⁺ + 2B
A²⁺ + 2e^– → AE° = + 0.34V and log₁₀ K = 15.6 at 300K for cell reactions find E° for
B¹ + e^– → B
(a) 0.80
(b) 1.26
(c) – 0.54
(d) – 10.94
Answer:
(a) 0.80

Samacheer Kalvi 12th Chemistry Electro Chemistry Short Answer

Question 1.
Define anode and cathode
Answer:

1. Anode: The electrode at which the oxidation occur is called anode.
2. Cathode: The electrode at which the reduction occur is called cathode.

Question 2.
Why does conductivity of a solution decrease on dilution of the solution?
Answer:
Conductivity always decreases with decrease in concentration (on dilution of the solution) both for weak as much as for strong electrolytes. ¡t is because the number of ions per unit volume that carry the current is a solution decreases on dilution.

Question 3.
State Kohlrausch Law. How is it useful to determine the molar conductivity of weak electrolyte at infinite dilution.
Answer:
Kohlrausch’s law:
It is defined as, at infinite dilution the limiting molar conductivity of an electrolyte is equal to the sum of the limiting molar conductivities of its constituent ions.

Determination of the molar conductivity of weak electrolyte at infinite dilution.
It is impossible to determine the molar conductance at infinite dilution for weak electrolytes experimentally. However, the same can be calculated using Kohlraushs Law. For example, the molar conductance of CH₃COOH, can be calculated using the experimentally determined molar conductivities of strong electrolytes HCI, NaCI and CH₃COONa.
Λ°_CH3COONa = λ°_Na⁺ + λ°_CH3COONa …….(1)
Λ°_HCl = λ°_H⁺ + λ°_Cl^– ………………(2)
Λ°_NaCl = λ°_Na⁺ + λ°_Cl^– …………….(3)
Equation (1) + Equation (2) – Equation (3) gives,
(Λ°_CH3COONa) + (Λ°_HCl) – (Λ°_NaCl) = λ°_H⁺ + λ°_CH3COONa = Λ°_CH3COONa

Question 4.
Describe the electrolysis of molten NaCI using inert electrodes.
Answer:
1. The electrolytic cell consists of two iron electrodes dipped in molten sodium chloride and they are connected to an external DC power supply via a key.

2. The electrode which is attached to the negative end of the power supply is called the cathode and the one is which attached to the positive end is called the anode.

3. Once the key is closed, the external DC power supply drives the electrons to the cathode and at the same time
pull the electrons from the anode.

Cell reactions:
Na⁺ ions are attracted towards cathode, where they combines with the electrons and reduced to liquid sodium.
Cathode (reduction)
Na⁺_(I) + e^–Na₍₁₎
E⁰ = – 2.7 1V
Similarly, Cl^– ions are attracted towards anode where they losses their electrons and oxidised to chlorine gas. Anode (oxidation)
2Cl^–₍₁₎ Cl_2(g) + 2e^–
E° = – 1 .36V
The overall reaction is,
2Na⁺_(l) + 2Cl^–_(l) → 2Na_(l) + Cl_2(g) (g)
E⁰ = 4.07 V

The negative E° value shows that the above reaction is a non spontaneous one. Hence, we have to supply a voltage greater than 4.07V to cause the electrolysis of molten NaCI. In electrolytic cell, oxidation occurs at the anode and reduction occur at the cathode as in a galvanic cell, but the sign of the electrodes is the reverse i.e., in the electrolytic cell cathode is -ve and anode is +ve.

Question 5.
State Faraday’s Laws of electrolysis.
Answer:
Faraday’s laws of electrolysis:
1. First law:
The mass of the substance (M) liberated at an electrode during electrolysis is directly proportional to the quantity of charge (Q) passed through the cell. M α Q

2. Second law:
When the same quantity of charge is passed through the solutions of different electrolytes, the amount of substances liberated at the respective electrodes are directly proportional to their electrochemical equivalents. M α Z

Question 6.
Describe the construction of Daniel cell. Write the cell reaction.
Answer:
The separation of half reaction is the basis for the construction of Daniel cell. It consists of two half cells.

Oxidation half cell:
The metallic zinc strip that dips into an aqueous solution of zinc sulphate taken in a beaker.

Reduction half cell:
A copper strip that dips into an aqueous solution of copper sulphate taken in a beaker.

Joining the half cell:
The zinc and copper strips are externally connected using a wire through a switch (k) and a load (example: volt meter). The electrolytic solution present in the cathodic and anodic compartment are connected using an inverted U tube containing a agar-agar gel mixed with an inert electrolyte such as Kl1, Na₂SO₄ etc.,

The ions of inert electrolyte do not react with other ions present in the half cells and they are not either oxidised (or) reduced at the electrodes. The solution in the salt bridge Voltmeter
cannot get poured out, but through which the ions can move into (or) out of the half cells. When the switch (k) closes the circuit, the electrons flows from zinc strip to copper strip. This is due to the following redox reactions which are taking place at the respective electrodes.

Anodic oxidation:
The electrode at which the oxidation occur is called the anode. In Daniel cell, the oxidation take place at zinc electrode, i.e., zinc is oxidised to Zn² ions and the electrons. The Zn² ions enters the solution and the electrons enter the zinc metal, then flow through the external wire and then enter the copper strip. Electrons are liberated at zinc electrode and hence it is negative ( – ve).
Zn(s) → Zn²⁺(aq) + 2e^– (loss of electron-oxidation)

Cathodic reduction:
As discussed earlier, the electrons flow through the circuit from zinc to copper, where the Cu²⁺ ions in the solution accept the electrons, get reduced to copper and the same get deposited on the electrode. Here, the electrons are consumed and hence it is positive (+ve).
Cu²⁺_(aq) + 2e^– → Cu_(s) (gain of electron-reduction)

Salt bridge:
The electrolytes present in two half cells are connected using a salt bridge. We have learnt that the anodic oxidation of zinc electrodes results in the increase in concentration of Zn²⁺ in solution. i.e., the solution contains more number of Zn²⁺ ions as compared to SO₄^2- and hence the solution in the anodic compartment would become positively charged.

Similarly, the solution in the cathodic compartment would become negatively charged as the Cu²⁺ ions are reduced to copper i.e., the cathodic solution contain more number of SO^2-₄ ions compared to Cu²⁺.

Completion of circuit:
Electrons flow from the negatively charged zinc anode into the positively charged copper electrode through the external wire, at the same time, anions move towards anode and cations are move towards the cathode compartment. This completes the
circuit.

Consumption of Electrodes:
As the Daniel cell operates, the mass of zinc electrode gradually decreases while the mass of the copper electrode increases and hence the cell will function until the entire metallic zinc electrode is converted in to Zn²⁺ the entire Cu²⁺ ions are converted in to metallic copper.
Daniel cell is represented as
Zn_(s)|Zn²⁺_(aq)||Cu²⁺_(aq)|Cu_(s)

Question 7.
Why is anode in galvanic cell considered to be negative and cathode positive electrode?
Answer:
A galvanic cell works basically in reverse to an electrolytic cell. The anode is the electrode where oxidation takes place, in a galvanic cell, it is the negative electrode, as when oxidation occurs, electrons are left behind on the electrode.

The anode is also the electrode where metal atoms give up their electrons to the metal and go into solution. The electron left behind on it render ¡t effectively negative and the electron flow goes from it through the wire to the cathode.

Positive aqueous ions in the solution are reduced by the incoming electrons on the cathode. This why the cathode is a positive electrode, because positive ions are reduced to metal atoms there.

Question 8.
The conductivity of a 0.01%M solution of a 1:1 weak electrolyte at 298K is 1.5 x 10^-4 S cm^-1.

1. molar conductivity of the solution
2. degree of dissociation and the dissociation constant of the weak electrolyte

Given that
λ⁰cation = 248.2 S cm² mol^-1
λ⁰anion = 51.8 S cm² mol^-1
Answer:
1. Molar conductivity
C = 0.01M
k = 1.5 x 10^-4 S cm^-1
(or)
K = 1.5 x 10^-2 S m^-1
\(\frac{\kappa \times 10^{-3}}{\mathrm{C}}\) S m^-1 mol^-1 m³ = \(\frac{1.5 \times 10^{-2} \times 10^{-3}}{0.01}\) S m² mol^-1
Λ_m = 1.5 x 10^-3 s m^-1

2. Degree of dissociation
α = \(\frac{\Lambda_{\mathrm{m}}}{\Lambda_{\infty}^{\circ}}\) (or) α = \(\frac{\Lambda_{\mathrm{m}}}{\Lambda_{\mathrm{m}}^{\circ}}\)
= (248.2 + 51.8)S cm² mol^-1
= 300 S cm² mol^-1
K_a = \(\frac{\alpha^{2} C}{1-\alpha}\)
= \(\frac{(0.05)^{2}(0.01)}{1-0.05}\)
K_a = 2.63 x 10^-5

Question 9.
Which of 0.1M HCI and 0.1 M KCI do you expect to have greater molar conductance and why?
Answer:
Compare to 0.1M HCI and 0.1 M KCI, 0.1M HCl has greater molar conductance.

1. Molar conductance of 0.1M HCl = 39.132 x 10^-3 S m² mol^-1.
2. Molar conductance of 0.1 M KCl = 12.896 x 10^-3 S m² mol^-1

Because, H⁺ ion in aqueous solution being smaller size than K⁺ ion and H⁺ ion have greater mobility than K ion. When mobility of the ion increases, conductivity of that ions also increases. Hence, 0. 1M HCI solution has greater molar conductance than 0.1 M KCI solution.

Question 10.
Arrange the following solutions in the decreasing order of specific conductance.

1. 0.01M KCI
2. 0.005M KCI
3. 0.1M KCI
4. 0.25 M KCI
5. 0.5 M KCI

Answer:
0.005M KCl > 0.01M KCI > 0.1M KCI > 0.25KCl > 0.5 KCI.
Specific conductance and concentration of the electrolyte. So if concentration decreases, specific conductance increases.

Question 11.
Why is AC current used instead of DC in measuring the electrolytic conductance?
Answer:
1. AC current to prevent electrolysis of the solution.

2. If we apply DC current to the cell the positive ions will be attracted to the negative plate and the negative ions to the positive plate. This will cause the composition of the electrolyte to change while measuring the equivalent conductance.

3. So DC current through the conductivity cell will lead to the electrolysis of the solution taken in the cell. To avoid such a electrolysis, we have to use AC current for measuring equivalent conductance.

Question 12.
0.1M NaCI solution is placed in two different cells having cell constant 0.5 and 0.25cm^-1 respectively. Which of the two will have greater value of specific conductance.
Answer:
The specific conductance values are same. Because the reaction (cation) of cell constant does not change.

Question 13.
A current of 1 .608A is passed through 250 mL of 0.5M solution of copper sulphate for 50 minutes. Calculate the strength of Cu²⁺ after electrolysis assuming volume to be constant and the current efficiency is 100%.
Answer:
Given, I = I .608A
t = 50 min (or) 50 x 60 = 3000 S
V = 250 mL
C = 0.5M
η = 100%
The number of Faraday’s of electricity passed through the CuSO₄ solution
Q = It
= Q = 1.608 x 3000
Q = 4824C
Number of Faraday’s of electricity = \(\frac { 4824C }{ 96500C }\) = 0.5F
Electrolysis of CuSO₄
Cu²⁺_(aq) + 2e^– → Cu_(s)
The above equation shows that 2F electricity will deposit 1 mole of Cu²⁺
0.5F electicity will deposit \(\frac { 1mol }{ 2F }\) x 0.5F = 0.025 mol
Initial number of molar of Cu²⁺ in 250 ml of solution = \(\frac { 1mol }{ 250mL }\) x 250mL = 0.125 mol
Number of molar of Cu²⁺ after electrolysis 0.125 – 0.025 = 0.1 mol
Concentration of Cu²⁺ = \(\frac { 0.1mol }{ 250mL }\) X 1000 mL = 0.4 M

Question 14.
Can Fe³⁺ oxidises Bromide to bromine under standard conditions?
Given:

Answer:
Required half cell reaction

E⁰_cell = (E⁰_ox) + (E⁰_red) = – 1.09 + 0.771 = – 0.319V
We know that ∆G° = – nFE⁰_cell
If E⁰_cell is -ve; ∆G is +ve and the cell reaction is non-spontaneous.
Hence, Fe³⁺ cannot oxidise Bromide to Bromine.

Question 15.
Is it possible to store copper sulphate in an iron vessel for a long time?
Given:

Answer:
E⁰_cell = (E⁰_ox) + (E⁰_red) = 0.44 V + 0.34V = 0.78V
These +ve E⁰_cell values shows that iron will oxidise and copper will get reduced i.e., the vessel
will dissolve. Hence it is not possible to store copper sulphate in an iron vessel.

Question 16.
Two metals M₁ and M₂ have reduction potential values of – xV and + yV respectively. Which will liberate H₂ in H₂SO₄?
Answer:
Metals having negative reduction potential acts as powerful reducing agent. Since M₁ has – xV, therefore M1 easily liberate H₂ in H₂SO₄. Metals having higher oxidation potential will liberate H₂ from H₂SO₄. Hence, the metal M₁ having + xV, oxidation potential will liberate H₂ from H₂SO₄.

Question 17.
Reduction potential of two metals M₁ and M₂ are

Predict which one Is better for coating the surface of iron.
Given:
Answer:
Oxidation potential of M₁ is more +ve than the oxidation potential of Fe which indicates that it will prevent iron from rusting.

Question 18.
Calculate the standard emf of the cell: Cd | Cd²⁺|| Cu²⁺ | Cu and determine the cell reaction. The standard reduction potentials of Cu²⁺ | Cu and Cd²⁺ | Cd are 0.34V and – 0.40 volts respectively. Predict the feasibility of the cell reaction.
Answer:
Cell reactions:

Cd(s) + 2e^– Cd²⁺ + Cu(s)
E⁰_cell = (E⁰_ox) + (E⁰_red) = 0.4 + 0.34
emf is +ve, so ∆G is (-)ve, the reaction is feasible.

Question 19.
In fuel cell H₂ and O₂ react to produce electricity. In the process, H₂ gas is oxidised at the anode and O₂ at cathode. If 44.8 litre of H₂ at 25°C and also pressure reacts in 10 minutes, what is average current produced? If the entire current is used for electro deposition of Cu from Cu²⁺, how many grams of Cu deposited?
Answer:
Oxidation at anode:
2H₂(g) + 4OH^– (aq) → 4H₂O (1) + 4e^–
1 mole of hydrogen gas produces 2 moles of electrons at 25°C and 1 atm pressure, 1 mole of hydrogen gas occupies = 22.4 litres
∴no. of moles of hydrogen gas produced = \(\frac{1 \mathrm{mole}}{22.4 \text { litres }}\) x 44.8 litres = 2 moles of hydrogen
∴2 of moles of hydrogen produces 4 moles of electro i.e., 4F charge. We know that Q = It
I = \(\frac { Q }{ t }\) = \(\frac{4 \mathrm{F}}{10 \mathrm{mins}}\) = \(\frac { 4×96500 }{ 10x60s }\)
I = 643.33 A
Electro deposition of copper
Cu²⁺_(aq) + 2e^– → Cu_(s)
2F charge is required to deposit
1 mole of copper i.e., 63.5 g
If the entire current produced in the fuel cell i.e., 4 F is utilised for electrolysis, then 2 x 63.5 i.e., 127.0 g copper will be deposited at cathode.

Question 20.
The same amount of electricity was passed through two separate electrolytic cells containing solutions of nickel nitrate and chromium nitrate respectively. If 2.935g of Ni was deposited in the first cell. The amount of Cr deposited in the another cell? Given: molar mass of Nickel and chromium are 58.74 and 52gm^-1 respectively.
Answer:
Ni²⁺ (aq) + 2e^– → Ni (s)
Cr²⁺(aq) + 3e^– → Cr(s)
The above reaction indicates that 2F charge is required to deposit 58.7 g of Nickel form nickel nitrate and 3F charge is required to deposit 52g of chromium. Given that 2.935 gram of Nickel is deposited 2F
The amount of charge passed through the cell = \(\frac { 2F }{ 58.7g }\) x 2.935g = 0.1F
If 0. IF charge is passed through chromium nitrate the amount of chromium deposited
= 52g x 0.IF = 1.733g

Question 21.
0.1M copper sulphate solution in which copper electrode is dipped at 25C. Calculate the electrode potential of copper.

Answer:
Given that
[Cu²⁺] = 0.1 M
E⁰_Cu²⁺|Cu = 0.34
E_cell = ?
Cell reaction is Cu²⁺(aq) + 2e^– → Cu (s)
E_cell = E⁰ – \(\frac { 0.0591 }{ n }\) log \(\frac{[\mathrm{Cu}]}{\left[\mathrm{Cu}^{2+}\right]}\) = 0.34 – \(\frac { 0.0591 }{ 2 }\) log \(\frac { 1 }{ 0.1 }\)
= 0.34 – 0.0296 = 0.31 V

Question 22.
For the cell Mg(s) | Mg²⁺(aq) || Ag⁺ (aq) | Ag (s), calculate the equilibrium constant at 25°C and maximum work that can be obtained during operation of cell. Given:

Answer:

E⁰_cell = (E⁰_ox) + (E⁰_red) = 2.37 + 0.80 = 3.17 V
Overall reaction
Mg + 2Ag⁺ → Mg²⁺ + 2Ag
∆G° = -nFE°
= – 2 x 96500 x 3.17
= – 6.118 x 10⁵ J
We know that W_max = ∆G°
W_max = + 6.118 x 10₅ J
Relationship between ∆G° and K_eq is,
∆G = – 2.303 RT logK_eq
∆G = – 2.303 x 8.314 x 298 log K_eq [25°C = 298 K]
log K_eq = \(\frac{6.118 \times 10^{5}}{2.303 \times 8.314 \times 298}\) = \(\frac{6.118 \times 10^{5}}{5705.84}\)
log K_eq = 107.223
K_eq = Antilog (107.223)

Question 23.
8.2 x 10¹² litres of water is available in a lake. A power reactor using the electrolysis of water in the lake produces electricity at the rate of 2 x 10⁶ Cs^-1 at an appropriate voltage. How many years would it like to completely electrolyse the water in the lake. Assume that there is no loss of water except due to electrolysis.
Answer:
Hydrolysis of water:
At anode: 2H₂O → 4H⁺ + O₂ + 4e^– …………..(1)
At cathode: 2H₂O + 2e^– → H₂ + 2OH^–
Overall reaction: 6H₂O → 4H^– + 4OH^– +2H₂ + O₂
(or)
Equation (1) + (2) x 2
= 2H₂O → 2H₂ + O₂
According to Faraday’s Law of electrolysis, to electrolyse two mole of Water
(36g ≃ 36 mL. of H₂O), 4F charge is required alternatively, when 36 mL of water is electrolysed,
the charge generated = 4 x 96500 C.
When the whole water which is available on the lake is completely electrolysed the amount of charge generated is equal to

Given that in 1 second, 2 x 10⁶ C is generated therefore, the time required to generate
96500 x 10¹⁵ C is = \(\frac{1 \mathrm{S}}{2 \times 10^{6} \mathrm{C}}\) x 96500 x 10¹⁵C = 48250 x 10⁹ S
Number of year = \(\frac{48250 \times 10^{9}}{365 \times 24 \times 60 \times 60}\) 1 year = 365 days
= 1.5299 x 10⁶
= 365 x 24 hours
= 365 x 24 x 60 min
= 365 x 24 x 60 x 60 sec

Question 24.
Derive an expression for Nernst equation.
Answer:
Nernst equation is the one which relates the cell potential and the concentration of the species involved in an electrochemical reaction.
Let us consider an electrochemical cell for which the overall redox reaction is,
Answer:
xA + yB = lC + mD
The reaction quotient Q is,
\(\frac{[\mathrm{C}]^{1}[\mathrm{D}]^{\mathrm{m}}}{[\mathrm{A}]^{\mathrm{x}}[\mathrm{B}]^{\mathrm{y}}}\)
We know that,
∆G = ∆G⁰ + RT ln Q
∆G = – nFE_cell
∆G⁰ = -nFE⁰_cell
equation (1) becomes
– nFE_cell = -nFE⁰_cell + RT ln Q
Subsitute the Q value in equation (2)
– nFE_cell = – nFE⁰_cell + RT ln \(\frac{[\mathrm{C}]^{1}[\mathrm{D}]^{\mathrm{m}}}{[\mathrm{A}]^{\mathrm{x}}[\mathrm{B}]^{\mathrm{y}}}\). ………..(3)
Divide the whole equation (3) by – nF
E_cell = E°_cell – \(\frac { RT }{ nF }\) ln \(\left(\frac{[\mathrm{C}]^{1}[\mathrm{D}]^{\mathrm{m}}}{[\mathrm{A}]^{\mathrm{x}}[\mathrm{B}]^{\mathrm{y}}}\right)\)
E_cell = E°_cell – \(\frac { 2.303RT }{ nF }\) log \(\left(\frac{[\mathrm{C}]^{1}[\mathrm{D}]^{\mathrm{m}}}{[\mathrm{A}]^{\mathrm{x}}[\mathrm{B}]^{\mathrm{y}}}\right)\) ……………(4)
This is called the Nernst equation.
At 25°C (298 K) equation (4) becomes,
E_cell = E°_cell – \(\frac { 2.303×8.314×298 }{ nx96500 }\) log \(\left(\frac{[\mathrm{C}]^{1}[\mathrm{D}]^{\mathrm{m}}}{[\mathrm{A}]^{\mathrm{x}}[\mathrm{B}]^{\mathrm{y}}}\right)\)
E_cell = E°_cell – \(\frac { 0.0591 }{ n }\) log \(\left(\frac{[\mathrm{C}]^{1}[\mathrm{D}]^{\mathrm{m}}}{[\mathrm{A}]^{\mathrm{x}}[\mathrm{B}]^{\mathrm{y}}}\right)\)

Question 25.
Write a note on sacrificial protection.
Answer:
In this method, the metallic structure to be protected is made cathode by connecting it with more active metal (anodic metal). So that all the corrosion will concentrate only on the active metal. The artificially made anode thus gradually gets corroded protecting the original metallic structure. Hence this process is otherwise known as sacrificial anodic protection. Al, Zn and Mg are used as sacrificial anodes.

Question 26.
Explain the function of H₂ – O₂ fuel cell.
Answer:
In this case, hydrogen act as a fuel and oxygen as an oxidant and the electrolyte is aqueous KOH maintained at 200°C and 20 – 40 atm. Porous graphite electrode containing Ni and NiO serves as the inert electrodes. Hydrogen and oxygen gases are bubbled through the anode and cathode, respectively.
Oxidation occurs at the anode:
2H_2(g)+ 4OH_-(aq) → 4H₂O₍₁₎ + 4e^–
Reduction occurs at the cathode O₂(g) + 2 H₂O(1) + 4e^– → 4 OH^– (aq)
The overall reaction is 2H₂(g) + O₂(g) → 2H₂O(1)
The above reaction is the same as the hydrogen combustion reaction, however, they do not react directly ie., the oxidation and reduction reactions take place separately at the anode and cathode respectively like H₂ – O₂ fuel cell. Other fuel cell like propane – O₂ and methane O₂ have also been developed.

Question 27.
Ionic conductance at infinite dilution of Al³⁺ and SO₄^2- are 189 and 160 mho cm² equiv^-1. Calculate the equivalent and molar conductance of the electrolyte Al₂(SO₄) at infinite dilution.
Answer:
1. Molar conductance

= (2 x 189) + (3 x 160)
= 378 + 480
= 858 mho cm² mol^-1

2. Equivalent conductnace

= \(\frac { 189 }{ 3 }\) + \(\frac { 160 }{ 2 }\)
= 143 mho cm² (g equiv)^-1

Samacheer Kalvi 12th Chemistry Electro Chemistry Evaluate Yourself

Question 1.
Calculate the molar conductance of 0.01M aqueous KCI solution at 25°C . The specific conductance of KCl at 25°C is 14.114 x 10^-2 Sm^-1.
Answer:
Concentration of KCI solution = 0.01 M.
Specific conductance (K) = 14.114 x 10^-2 S m^-1
Molar conductance (Λ_m) = ?
Λ_m = \(\frac{\kappa \times 10^{-3}}{M}\) = \(\frac{14.114 \times 10^{-2} \times 10^{-3}}{0.01}\)
S m^-1 mol^-1 m³
Λ_m = 14.114 x 10^-5 x 10² = 14.114 x 10^-3 Sm² mol^-1

Question 2.
The resistance of 0.15M solution of an electrolyte is 50. The specific conductance of the solution is 2.4 Sm^-1. The resistance of 0.5 N solution of the same electrolyte measured using the same conductivity cell is 480Ω. Find the equivalent conductivity of 0.5 N solution of the electrolyte.
Answer:
Given that R₁ = 50Ω
R₂ = 480Ω
K₁ =2.4Sm^-1
K₂ = ?
N₁ = 0.15N
N₂ = 0.5N

= 5 x 10^-4sm² gram equivalent^-1
We know that
\(\frac{\text { Cell constant }}{\mathrm{R}}\)
\(\frac{\kappa_{2}}{\kappa_{1}}\) = \(\frac{R_{1}}{R_{2}}\)
k₂ = k₁ x \(\frac{R_{1}}{R_{2}}\) = 2.4 Sm^-1 x \(\frac{50 \Omega}{480 \Omega}\) = 0.25 Sm^-1

Question 3.
The emf of the following cell at 25°C is equal to 0.34v. Calculate the reduction potential of copper electrode.
Pt(s) | H₂(g,1atm) | H⁺ (aq,1M) || Cu²⁺(aq,1M) | Cu(s)
Answer:
SHE Value is zero
E°_cell = E°_R – E°_L
= 0.34 – 0 = 0.34V
The reduction potential of copper electrode = 0.34V

Question 4.
Using the calculated emf value of zinc and copper electrode, calculate the emf of the following cell at 25°C.
Zn (s) | Zn²⁺ (aq, 1M) || Cu²⁺(aq, 1M) | Cu (s)
Answer:
E°_cell = E°_R – E°_L
E_zn/zn²⁺ = 0.76V
E_Cu/Cu²⁺ = 0.76V
E°_cell = 0.76 – (- 0.34V)
E°_cell = 0.76 – (- 0.34)
E°_cell = + 1.1 V

Question 5.
Write the overall redox reaction which takes place in the galvanic cell,
Pt(s) | Fe²⁺(aq),Fe²⁺(aq) || MnO^–₄(aq), H⁺(aq), Mn²⁺(aq) || Pt(s)
Answer:
At Anode half cell – 5Fe²⁺_(aq) → 5Fe³⁺_(aq) + 5e^–
At cathode half cell – MnO^–_4(aq) + 8H⁺_(aq) + 5e^– → Mn²⁺_(aq) + 4H₂O₍₁₎
Overall redox reaction – 5Fe²⁺_(aq) + MnO^–₄(aq) + 8H⁺(aq) → 5Fe³⁺_(aq) + Mn²⁺_(aq) + 4H₂O₍₁₎

Question 6.
The electrochemical cell reaction of the Daniel cell is
Zn (s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu_(s)
What is the change in the cell voltage on increasing the ion concentration in the anode compartment by a factor 10?
Answer:
Zn (s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu_(s)
ln the case E°_cell = 1.1V
Reaction quotient Q for the above reaction is, Q = \(\frac{\left[\mathrm{Zn}^{2+}\right]}{\left[\mathrm{Cu}^{2+}\right]}\)
E_cell = E°_cell – \(\frac { 0.0591 }{ n }\) log \(\frac{\left[Z n^{2+}\right]}{\left[C u^{2+}\right]}\)
If suppose concentration of Cu²⁺ is 1 .OM then the concentration of Zn²⁺ is 10M (why because,
ion concentration in the anode compartment increased by a 10 factor)
E_cell = 1.1 – \(\frac { 0.0591 }{ n }\) log \((\frac { 10 }{ 1 })\)
= 1.1 – 0.02955             ……………….(1)
= 1.070 V (cell voltage decreased)
Thus, the initial voltage is greater than E° because Q < 1. As the reaction proceeds, [Zn²⁺] in the anode compartment increases as the zinc electrode dissolves, while [Cu²⁺] in the cathode compartment decreases as metallic copper is deposited on the electrode.

During this process, the Q = [Zn²⁺] [Cu²⁺] steadily increases and the cell voltage therefore steadily decreases. [Zn²⁺] will continue to increase in the anode compartment and [Cu²⁺] will continue to decrease in the cathode compartment. Thus the value of Q will increase further leading to a further
decrease in value.

Question 7.
A solution of a salt of metal was electrolysed for 150 minutes with a current of 0.15 amperes. The mass of the metal deposited at the cathode is 0.783g. calculate the equivalent mass of the metal.
Answer:
Given,
I = 0.15 amperes
t = 150 mins
= t = 15O x 6Osec
= t = 9000sec
Q = It
= Q = 0.15 x 9000 coulombs
= Q = 1350 coulombs
Hence, 135 coulombs of electricity deposit is equal to 0.783g of metal.
96500 coulombs of electricity, \(\frac { 0.783 x 96500 }{ 1350 }\) = 55.97 gm of metal
Hence equivalent mass of the metal is 55.97

Samacheer Kalvi 12th Chemistry Electro Chemistry Example Problems

Question 1.
A conductivity cell has two platinum electrodes separated by a distance 1.5 cm and the cross sectional area of each electrode is 4.5 sq cm. Using this cell, the resistance of 0.5 N electrolytic solution was measured as 15?. Find the specific conductance of the solution.
Solution.
k = \(\frac { 1 }{ 15Ω }\) x \(\frac{1.5 \times 10^{-2} \mathrm{m}}{4.5 \times 10^{-4} \mathrm{m}^{2}}\) = 2.22S m^-1
l = 1.5cm = 1.5 x 10²m
A = 4.5 cm² x (10^-4)m²
R = 15Ω

Question 2.
Calculate the molar conductance of 0.025M aqueous solution of calcium chloride at 25°C. The specific conductance of calcium chloride is 12.04 x 10²S m³.
Answer:
Molar conductance
_Λm = \(\frac{\left(\mathrm{Sm}^{-1}\right) \times 10^{-3}}{\mathrm{M}}\) mol^-1 m³
= \(\frac{\left(12.04 \times 10^{-2} \mathrm{Sm}^{-1}\right) \times 10^{-3}}{0.025}\) mol^-1 m³ = 581 . 6 10^-2 S m² mol¹

Question 3.
The resistance of a conductivity cell is measured as 190Ω using 0.1M KCI solution (specific conductance of 0.1M KCI is 1.3 Sm^-1). When the same cell is filled with 0.003M sodium chloride solution, the measured resistance is 6.3K?. Both these measurements are made at a particular temperature. Calculate the specific and molar conductance of NaCl solution.
Answer:
Given that
K = 1.3 S m^-1 (for 0.1 M KCI solution)
R = 190Ω
\(\left(\frac{l}{A}\right)\) = k.R = (1.3 S m^-1) (190?) = 247m^-1
k_(NaCl) = \(\frac{1}{\mathrm{R}_{(\mathrm{NaCT})}}\)\(\left(\frac{l}{A}\right)\) = \(\frac{1}{6.3 \mathrm{K} \Omega}\) (247m^-1)
= 39.2 x 10^-3Sm^-1
_Λm = \(\frac{\kappa \times 10^{-3} \mathrm{mol}^{-1} \mathrm{m}^{3}}{\mathrm{M}}\) = \(\frac{39.2 \times 10^{-3}\left(\mathrm{Sm}^{-1}\right) \times 10^{-3}\left(\mathrm{mol}^{-1} \mathrm{m}^{3}\right)}{0.003}\)
_Λm = 13.04 x 10^-3Sm² mol^-1

Question 4.
The net redox reaction of a galvanic cell is given below
2 Cr _(s) + 3Cu²⁺_(aq) → 2Cr³⁺_(aq) + 3Cu_(s)
Write the half reactions and describe the cell using cell notation.
Answer:
Anodic oxidation: 2Cr_(s) → 2Cr³⁺_(aq) + 6e^– …………..(1)
Cathodic reduction: 3Cu²⁺ + 6e^– → 3Cu_(s) ………….(2)
Cell Notation is: Cr_(s) | CI³⁺_(aq) || Cu²⁺_(aq) | Cu_(s)

Question 5.
Let us calculate the emf of the following cell at 25°C using Nernst equation.
Cu (s) | Cu²⁺(0.25 aq, M) || Fe³⁺(0.05 aq M) | Fe²⁺(0.1 aq M) | pt(s)
Answer:
Given:
Half reactions are
Cu (s) → Cu²⁺(aq) + 2e^– ……………(1)
2 Fe³⁺(aq) + 2e^– → 2Fe²⁺(aq) ……………(2)
the overall reaction is Cu (s) + 2 Fe³⁺(aq) → Cu²⁺(aq) + 2Fe²⁺(aq), and n = 2
Apply Nernst equation at 25°C

Given standard reduction potetial of Cu²⁺ | Cu is o.34

Question 6.
A solution of silver nitrate Is electrolysed for 20 minutes with a current of 2 amperes. Calculate the mass of silver deposited at the cathode.
Answer:
Electrochemical reaction at cathode is Ag⁺ + e^– Ag (reduction)
m = ZIt
m = \(\frac{108 \mathrm{gmol}^{-1}}{96500 \mathrm{Cmol}^{-1}} \times 2400 \mathrm{C}\)
m = 2.68 g
z = \(\frac{\text { molarmass of } \mathrm{Ag}}{(96500)}\) = \(\frac{108}{1 \times 96500}\)
I = 2Ag
t = 20 x 60s = 1200s
It = 2A x 1200S = 2400C

Samacheer Kalvi 12th Chemistry Electro Chemistry Additional Questions

Samacheer Kalvi 12th Chemistry Electro Chemistry 1 Marks Questions And Answers

I. Choose the best answer and write it.

Question 1.
Which one of the following is an example of conductor?
(a) PVC
(b) Bakelite
(c) Aluminium
(d) Rubber
Answer:
(c) Aluminium

Question 2.
Which one of the following can act as an insulator?
(a) Bakelite
(b) Aluminium
(c) Copper
(d) NaCI Solution
Answer:
(a) Bakelite V

Question 3.
Which form of energy is converted to electrical energy in batteries?
(a) tidal energy
(b) Chemical energy
(c) mechanical energy
(d) atomic energy
Answer:
(b) Chemical energy

Question 4.
Electro chemical reactions are generally ………..
(a) Reduction reactions
(b) oxidation reactions
(c) Redox reactions
(d) condensation reactions
Answer:
(c) Redox reactions

Question 5.
Consider the following statements.
Answer:
(i) Energy can neither be created nor be destroyed but one form of energy can be converted to another form
(ii) In batteries, electrical energy is converted to chemical energy.
(iii) Electrochemjcal reactions are redox reactions.

Which of the above statement is / are not correct?
(a) i & ii only
(b) ii only
(c) i only
(d) iii only
Answer:
(b) ii only

Question 6.
Which one of the following represents Ohm’s law?
(a) V = IR
(b) R = \(\frac { 1 }{ V }\)
(c) I = \(\frac { V }{ R }\)
(d) R = VI
Answer:
(a) V = IR

Question 7.
The unit of resistivity is …………
(a) Ω m^-1
(b) Ω m
(c) m^-1Ohm²
(d) Ω^-1m^-1
Answer:
(b) Ω m

Question 8.
When cell constant is unit, the resistance is known as …………
(a) specific resistance
(b) conductance
(c) specific conductance
(d) equivalent conductance
Answer:
(a) specific resistance

Question 9.
The unit of specific resistance is equal to ………..
(a) Ohm metre
(b) Ohm^-1 metre
(c) Ohm^-1 metre^-1
(d) Ohm
Answer:
(a) Ohm metre

Question 10.
Which is the SI unit of conductance?
(a) Siemen^-1 (or) S^-1
(b) Siemen (or) S
(c) Sm^-1
(d) S^-1m^-1
Answer:
(b) Siemen (S)

Question 11.
Which one of the following represents specific conductance (kappa)?
(a) \(\frac { I }{ C }\) . \(\frac { l }{ a }\)
(b) \(\frac { I }{ P }\) . \(\frac { a }{ I }\)
(c) \(\frac { 1 }{ 2 }\) . \(\frac{a}{l^{2}}\)
(d) \(\frac { I }{ P }\) . \(\frac { l }{ a }\)
Answer:
(d) \(\frac { I }{ P }\) . \(\frac { l }{ a }\)

Question 12.
Which one is the unit of specific conductance?
(a) Ohm m
(b) Ohm^-1 m
(c) Ohm m^-1
(d) Ohm^-1 m^-1.
Answer:
(d) Ohm^-1m^-1

Question 13.
Which one of the following formula represents equivalent conductance?
(a) \(\frac { I }{ P }\).\(\frac { l }{ a }\)
(b) \(\frac { I }{ P }\).\(\frac { A }{ l }\)
(c) C x \(\frac { l }{ a }\)
(d) \(\frac{\kappa \times 10^{-3}}{N}\)
Answer:
(d) \(\frac{\kappa \times 10^{-3}}{N}\)

Question 14.
The unit of equivalent conductance is …………
(a) Sm²g equivalenr’
(b) Sm^-1
(c) Ohm^-1m^-1
(d) Ohm m
Answer:
(a) Sm²g equivalent^-1

Question 15.
Consider the following statements:
(i) Solvent of higher dielectric constant show very low conductance in solution.
(ii) Conductance is directly proportional to viscosity of the medium.
(iii) Molar conductance of a solution increases with increase in dilution.
Which of the above statement is / are correct?
(a) (i) & (ii)
(b) (ii) and (iii)
(c) (iii) only
(d) (i) only
Answer:
(c) (iii) only

Question 16.
Consider the following statements:
(i) If the temperature of the electrolytic solution increases, conductance decreases.
(ii) Conductivity increases with the decrease in viscosity.
(iii) Molar conductance of a solution decreases with increase in dilution.
Which of the above statement is / are not correct?
(a) (i) & (iii)
(b) (i) and (ii)
(c) (iii) only
(d) (ii) only
Answer:
(a) (i) & (iii)

Question 17.
Which one of the following is used to measure conductivity of ionic solutions?
(a) metre scale
(b) wheat stone bridge
(c) Dynamo
(d) Ammeter
Answer:
(b) wheat stone bridge

Question 18.
Which of the following is used to calculate the conductivity of strong electrolytes?
(a) Kohlraush’s law
(b) Henderson equation
(c) Debye-Huckel and Onsagar equation
(d) Ostwald’s dilution law
Answer:
(c) Debye-Huckel and Onsagar equation

Question 19.
Which one of the following represents Debye-Huckel and Onsagar equation?

Answer:

Question 20.
The value of A in Debye – Huckel and Onsagar equation is ……….

Answer:

Question 21.
The value of B in Debye Huckel and onsagar equation is …………

Answer:

Question 22.
Kohlrausch’s law is applied to calculate
(a) molar conductance at infinite dilution of a weak electrolyte
(b) degree of dissociation of weak electrolyte
(c) solubility of a sparingly soluble salt
(d) all the above
Answer:
(d) all the above

Question 23.
In which of the following interconversion of electrical energy into chemical energy and vice versa take place?
(a) electrochemical cell
(b) electric cell
(c) Dynamo
(d) AC generator
Answer:
(a) electrochemical cell

Question 24.
Consider the following statements:
(i) In Galvanic cell, chemical energy is’converted into electrical energy.
(ii) In electrolytic cell, electrical energy is converted into chemical energy.
(iii) In voltaic cell, electrical energy is converted into chemical energy.

Which of the above statement is / are not correct?
(a) (i) & (ii)
(b) (iii) only
(c) (ii) only
(d) (i) only
Answer:
(b) (iii) only

Question 25.
In Galvanic cell, the Zinc metal strip placed gets ………….
(a) Oxidised
(b) reduced
(c) hydrolysed
(d) condensed
Answer:
(a) Oxidised

Question 26.
Consider the following statements:
(i) In Galvanic cell, Zinc is oxidised to Zn²⁺ ions and Cu²⁺ ions are reduced to copper
(ii) In Galvanic cell, Zn²⁺ ions are reduced to Zinc and copper is oxidised to Cu²⁺ ions
(iii) In Galvanic cell, Zn and copper both get oxidised.
Which of the above statement is / are correct?
(a) (i) only
(b) (ii) & (iii)
(c) (ii) only
(d) (iii) only
Answer:
(a) (i) only

Question 27.
The salt bridge used in Daniel cell contains
(a) Na₂SO₄ + NaCl
(b) Agar-Agar gel + Na₂SO₄
(c) Silica gel + CuSO₄
(d) ZnSO₄ + CuSO₄
Answer:
(b) Agar-Agar gel + Na₂SO₄

Question 28.
Consider the following statements.
(i) In Daniel cell, when the switch (k) closes the circuit, the electrons flow from Zinc strip to copper strip.
(ii) In Daniel cell, when the switch (k) closes the circuit, the electrons flow from copper strip to Zinc strip
(iii) In Daniel cell, when the Switch (k) opens the circuit, the electrons flow from Zinc to copper.
Which of the above statement is / are correct?
(a) (i) only
(b) (ii) & (iii)
(c) (ii) only
(d) (iii) only
Answer:
(a) (i) only

Question 29.
Which one of the following can act as an inert electrode?
(a) Graphite
(b) Copper
(c) Platinum
(d) either a (or) e
Answer:
(a) either a (or) c

Question 30.
The SI unit of cell potential is ………….
(a) Ampere
(b) Ohm
(c) Volt
(d) Ohm^-1
Answer:
(c) Volt

Question 31.
The emf of Daniel cell Zn_(s) + Zn²⁺_aq(1m) || Cu²⁺_aq(1m) | Cu_(S) iS equal to …………
(a) – 1.107 Volts
(b) 1.107 Volts
(c) 3.4 Volt
(d) 7.6 Volt
Answer:
(b) 1.107 Volts

Question 32.
Which instrument is used to measure potential difference?
(a) Ammeter
(b) Voltmeter
(c) Wheat stone bridge
(d) metre bridge
Answer:
(b) Voltmeter

Question 33.
The value of EMF of standard hydrogen electrode at 25°C is …………
(a) maximum
(b) zero
(c) negative
(d) positive
Answer:
(b) zero

Question 34.
The electrode used in SHE is made of ………….
(a) graphite
(b) copper
(c) platinum
(d) iron
Answer:
(c) Platinum

Question 35.
What is the charge of one electron?
(a) 1.602 x 10¹⁹C
(b) 1.6 x 10^-19C
(c) 9645C
(d) 96488C
Answer:
(b) 1.6 x 10^-19C

Question 36.
The maximum work that can be obtained from a galvanic cell is ………..
(a) + nFE
(b) – nFE
(c) 2F
(d) 96500 F
Answer:
(b) – nFE

Question 37.
For all spontaneous cell reactions, the value of ?G should be ………….
(a) constant
(b) zero
(c) negative
(d) positive
Answer:
(c) negative

Question 38.
The value of one Faraday is equal to …………..
(a) 96400 C
(b) 96500 C
(c) 1 .602 x 10^-19C
(d) 1 .602 x 10¹⁹C
Answer:
(b) 96500 C

Question 39.
The relationship between standard free energy change and equilibrium constant is expressed as ………..
(a) ΔG° = -RTInk_eq
(b) ΔG = RTlnk_eq
(c) ΔG° = \(-\frac{1}{\mathrm{RT} \ln \mathrm{k}_{\mathrm{eq}}}\)
(d) ΔG = RTlog_eq
Answer:
(a) ΔG° -RThilc

Question 40.
Which equation relates the cell potential and the concentration of the species involved in an electro chemical reaction?
(a) Henderson equation
(b) Arrhenius equation
(c) Debye Huckel Onsagar equation
(d) Nemst equation
Answer:
(a) Nernst equation

Question 41.
Which one of the following is Nernst equation.

Answer:

Question 42.
Gibbs free energy can be related to cell emf as follows.
(a) ΔG° = – nFE_cell
(b) ΔG° = – nFE°_cell
(c) ΔG = nFE_cell
(d) ΔG° = nFE°_cell
Answer:
(b) ΔG° = – nFE°_cell

Question 43.
Which one of the following represents Faraday’s first law?
(a) m = ZIt
(b) m = \(\frac { Z }{ It }\)
(c) m = \(\frac { It }{ Z }\)
(d) Z = mIt
Answer:
(a) m = ZIt

Question 44.
When 1 coulomb of electric current is passed the amount of substance deposited or liberated is known as ………..
(a) equivalent mass
(b) electro chemical equivalent
(c) molar mass
(d) 1 Faraday
Answer:
(b) electro chemical equivalent

Question 45.
The value of electro chemical equivalent is equal to ………..
(a) \(\frac{96500}{\text { Equivalent mass }}\)
(b) \(\frac{96500}{\text { Molar mass }}\)
(c) \(\frac{\text { Molar mass }}{96500}\)
(d) \(\frac{\text { Equivalent mass }}{96500}\)
Answer:
(d) \(\frac{\text { Equivalent mass }}{96500}\)

Question 46.
The mathematical expression of Faraday’s second law is …………
(a) m = ZIt
(b) \(\frac{m_{1}}{E_{1}}=\frac{m_{2}}{E_{2}}=\frac{m_{3}}{E_{3}}\)
(c) \(\frac{m_{1}}{Z_{1}}=\frac{m_{2}}{Z_{2}}=\frac{m_{3}}{Z_{3}}\)
(d) \(Z=\frac{m}{I t}\)
Answer:
(c) \(\frac{m_{1}}{Z_{1}}=\frac{m_{2}}{Z_{2}}=\frac{m_{3}}{Z_{3}}\)

Question 47.
Which one of the following is used in cell phone, dry cell in flashlight?
(a) Zn – Cu battery
(b) Li – ion battery
(c) Ag – Cu battery
(d) Na, NaCI battery
Answer:
(b) Li – ion battery

Question 48.
The primary batteries are ………..
(a) rechargeable
(b) non – rechargeable
(c) reversible
(d) renewable
Answer:
(b) non – rechargeable

Question 49.
Consider the following statements.
(i) The secondary batteries are rechargeable
(ii) Primary batteries are non – rechargeable
(iii) Batteries are used as a source of AC current at a constant voltage.
Which of the above statement is I are not correct?
(a) (i) & (ii)
(b) (iii) only
(c) (i) only
(d) (ii) only
Answer:
(b) (iii) only

Question 50.
The anode and cathode used in Leclanche cell are ………… respectively.
(a) Zinc, Graphite rod with MnO₂
(b) Graphite rod in MnO₂ and Zinc container
(c) Zn container and copper rod
(d) Copper container and Zinc rod
Answer:
(a) Zinc, Graphite rod with MnO₂

Question 51.
Which electrolyte is used in Leclanche cell?
(a) ZnSO₄ + CuSO₄
(b) NH₄CI + ZnCl₂
(c) NaCI + CuSO₄
(d) MnSO₄ + MnO₂
Answer:
(b) NH₄Cl + ZnCl₂

Question 52.
Which one of the following is used as cathode in Mercury button cell?
(a) Zinc
(b) Copper
(c) Zinc amalgamated with mercury
(d) HgO mixed with graphite
Answer:
(c) Zinc amalgamated with mercury

Question 53.
Which one of the following is used as anode in Mercury button cell?
(a) HgO mixed with graphite
(b) Zinc amalgamated with mercury
(c) Copper amalgamated with Mercury
(d) HgO mixed with Copper
Answer:
(a) HgO mixed with graphite.

Question 54.
The value of cell emf of Mercury button cell is ………..
(a) 1.35V
(b) – 076V
(c) 0.34V
(d) 100V
Answer:
(a) 1.35 V
Which one of the following is used in pacemakers, cameras and electronic watches?
(a) Li-ion battery
(b) Leclanche cell
(c) Galvanic cell
(d) Mercurry button cell
Answer:
(d) Mercury button cell

Question 56.
The electrolyte used in Mercury button cell is ………….
(a) Paste of kOH and ZnO
(b) CuSO₄ + ZnSO₄
(c) NaCl + MgCl₂
(d) NH₄CI + ZnCl₂
Answer:
(a) Paste of kOH and ZnO

Question 57.
Which of the following is an example of secondary batteries?
(a) Mercury button cell
(b) Leclanche cell
(c) Lead storage battery
(d) Daniel cell
Answer:
(c) Lead storage battery

Question 58.
Which of the following act as cathode and anode in Lead storage battery?
(a) Lead plate bearing PbO₂, spongy Lead
(b) Spongy lead, lead plate bearing PbO₂
(c) Lead Copper
(d) Mercury oxide, PbO
Answer:
(a) Lead plate bearing PbO₂, Spongy lead

Question 59.
Which one of the following is used as an electrolyte Lead storage battery?
(a) PbSO₄
(b) H₂SO₄
(c) CuSO₄
(d) HNO₃
Answer:
(b) H₂SO₄

Question 60.
The emf of lead storage battery is …………
(a) +1.1 V
(b) 2.4V
(c) 2V
(d) 11 . 2V
Answer:
(c) 2 V

Question 61.
The Lead storage battery is used in …………
(a) pacemakers
(b) automobiles
(c) electronic watches
(d) flash light
Answer:
(b) automobiles

Question 62.
Which one of the following is used in automobiles, trains and in inverters?
(a) Lithium ion battery
(b) Mercurry button cell
(c) Lead storage battery
(d) Leclanche cell
Answer:
(c) Lead storage battery

Question 63.
Which one of the following is used as an anode in Lithium ion battery?
(a) Porous graphite
(b) Lithium
(c) CoO₂
(d) Copper
Answer:
(a) Porous graphite

Question 64.
which one of the following is used as cathode in Lithium ion battery?
(a) Porous graphite
(b) Lithium
(c) CoO₂
(d) Chromium
Answer:
(c) CoO₂

Question 65.
Which one of the following is used in cellular phones, Laptop computers and in digital camera?
(a) Mercury button cell
(b) Lithium – ion battery
(c) H₂O₂ fuel cell
(d) Leclanche cell
Answer:
(b) Lithium – ion battery

Question 66.
Which one of the following is used as an electrolyte in H₂O₂ fuel cell?
(a) Aqueous CuSO₄
(b) Aqueous CoO₂
(c) Aqueous KOH
(d) NH₄CI + ZnCI₂
Answer:
(c) Aqueous KOH

Question 67.
Which one of the following is an example for electrochemical process?
(a) Chrome plating
(b) Rusting of iron
(c) Galvanisation
(d) All the above
Answer:
(a) All the above

Question 68.
The formula of rust is ………..
(a) Fe₂O₃
(b) Fe₂O₃.xH₂O
(c) FeO
(d) FeO.xH₂O
Answer:
(b) Fe₂O₃.xH₂O

Question 69.
Which one of the following is / are very important for rusting’?
(a) Oxygen
(b) Water
(c) Both a & b
(d) H₂O
Answer:
(c) Both a & b

Question 70.
The electro plating of Zinc over a metal is called …………..
(a) Electrolysis
(b) Redox reaction
(c) Galvanisation
(d) Passivation
Answer:
(c) Galvanisation

Question 71.
Consider the following statements.
(i) The standard reduction potential (E°) is a measure of oxidising tendency of the species.
(ii) The standard oxidation potential (E°) is a measure of oxidising tendency of the species.
(iii) The standard oxidation potential (E°) is a measure of redox tendency of the species.
Which of the above statement is / are not correct?
(a) (i) only
(b) (ii) only
(c) (ii) & (iii)
(d) (iii) only
Answer:
(c) (ii) & (iii)

Question 72.
On the basis of the electrochemical theory of aqueous corrosion, the reaction occuring at the cathode is …………

Answer:

Hint:
2H⁺_(aq) + 2e^– → 2H₂
2H⁺ + \(\frac { 1 }{ 2 }\)O₂ → H₂O
2H⁺ + \(\frac { 1 }{ 2 }\)O₂ +2e^– → H₂O
Balancing the above equation
4H⁺_(aq) + O₂ + 4e^– → 2H₂O

Question 73.
The standard reduction potential for the half reactions are as ………..
Zn → Zn²⁺ + 2e^– E° = +0.76V
Fe → Fe²⁺ + 2e^–E° = + 041 V.
So for cell reaction F²⁺ + Zn → Zn²⁺ + Fe is ………….
(a) – 0.35V
(b) +0.35V
(c) +1.17V
(d) – 1.117V
Answer:
(b) +0.35V
Hint:
In the reaction F²⁺ + Zn° → Zn²⁺ + Fe°
emf = E_cathode – E_anode
= – 0.41 – (- 0.76)
= – 0.41 + 0.76
emf = + 0.35V

Question 74.
The standard emf for the given cell reaction Zn + Cu²⁺ → Cu + Zn²⁺ is 1.10V at 25°C. The emf for the cell reaction when 0.1 M Cu²⁺ and 0.1 M Zn²⁺ solutions are used at 25°C is ……….
(a) 1.10V
(b) 0.110V
(c) – 1.10V
(d) – 110V
Answer:
(a) 1.10V
Hint:
E_cell = E°_cell – \(\frac { 0.0592 }{ 2 }\) log\(\frac{\left(Z n^{2+}\right)}{\left(C u^{2+}\right)}\)
= 1.10 – \(\frac { 0.0592 }{ 2 }\) log \(\frac { 0.1 }{ 0.1 }\)
= 1.10 – \(\frac { 0.0592 }{ 2 }\) log 1
= 1.10 – \(\frac { 0.0592 }{ 2 }\) x 0
= 1.10V

Question 75.
Which amount of chlorine gas liberated at anode, if 1 ampere current is passed for 30 minutes from NaCI solution?
(a) 0.66 moles
(b) 0.33 moles
(c) 0.66 g
(d) 0.33 g
Answer:
(c) 0.66 g
Hint:
2Cl^– → Cl₂ + 2e^–
Q = It.
Amount of current passed = 1 x 30 x 60 = 1800C
The amount of Cl₂ liberated by passing 1800 coulomb of electric charge
= \(\frac{1 \times 1800 \times 71}{2 \times 96500}\)
= 0.66g

Question 76.
When Zinc piece is kept in CuSO₄ solution the copper gets precipitated due to standard potential of Zinc is …………
(a) > copper
(b) < copper
(c) > Sulphate
(d) < Sulphate
Answer:
(b) < copper
Hint:
Standard potential of zinc < copper.

Question 77.
Which equation shows the relation between electrode potential (E) standard electrode potential (E°) and concentration of ions in solution is ………..
(a) Kohlrausch’s equation
(b) Nernst equation
(c) Ohm’s equation
(d) Faraday’s equation
Answer:
(b) Nernst equation

Question 78.
The standard electrode potential of SHE at 298K is ………
(a) 0.05 V
(b) 0.01 V
(c) 0.0 V
(d) 0.11 V
Answer:
(c) 0.0 V

Question 79.
The reaction Zn²⁺ + 2e^– → Zn has a standard potential of – 0.76 V. This means
(a) Zn cannot replace hydrogen from acids
(b) Zn is a reducing agent
(c) Zn is an oxidising agent
(d) Zn²⁺ is a reducing agent
Answer:
(b) Zn is a reducing agent.
Hint:
Since E⁰_Zn²⁺/Zn is negative, so Zn has a greater tendency to be oxidised than hydrogen. Hence it can act as reducing agent.

Question 80.
K, Ca and Li metals may be arranged in the decreasing order of their standard electrode potentials as ……..
(a) K, Ca, Li
(b) Ca, K, Li
(c) Li, Ca, K
(d) Ca, Li, K
Answer:
(b) Ca, K, Li

Question 81.
The correct order of chemical reactivity with water according to electrochemical series ………….
(a) K > Mg > Zn > Cu
(b) Mg > Zn > Cu > K
(c) K > Zn > Mg > Cu
(d) Cu > Zn > Mg > K
Answer:
(a) K > Mg > Zn > Cu
Hint:
The standard reduction potential of K⁺, Mg²⁺, Zn²⁺, Cu²⁺ increases in this order.

Question 82.
For a spontaneous reaction, the ΔG, the equilibrium constant (K) and E°_cell will be respectively
(a) ve, > 1, + ve
(b) + ve , > 1, – ve
(c) – ve, < 1, – ve (d) – ve, > 1, – ve
Answer:
(a) – ve, > 1, + ve.

Question 83.
E° values of mg²⁺/mg is – 2.37 V, Zn²⁺/ Zn is – 0.76V, and Fe²⁺ / Fe is – 0.44 V. Which of the following statement is correct?
(a) Zn will reduce Fe²⁺
(b) Zn will reduce mg²⁺
(c) mg oxidises Fe
(d) Zn oxidises Fe
Answer:
(a) Zn will reduce Fe²⁺
Hint:
E⁰_Zn²⁺/Zn<E⁰_Fe²⁺/Fe So Zn will reduce Fe²⁺. Zinc cannot reduce Mg²⁺ because
\(\mathbf{E}_{\mathbf{Z n}^{2+} / \mathbf{z n}}^{\circ}>\mathbf{E}_{\mathrm{Mg}^{2+} / \mathrm{Mg}}^{\circ}\) On similar reason mg and Zn cannot oxidise Fe.

Question 84.
In which cell, the free energy of a chemical reaction is directly converted into electricity?
(a) Leclanche cell
(b) Fuel cell
(c) Lead storage battery
(d) Lithium ion battery
Answer:
(b) Fuel cell

Question 85.
Which of the following has the highest electrode potential?
(a) Li
(b) Cu
(c) Au
(d) Al
Answer:
(c)Au

Question 86.
Consider the following statements.
(i) A salt bridge is used to eliminate liquid junction potential
(ii) The Gibbs free energy change ∆G is related with electro motive force (E) as ∆G = – nFE.
(iii) Nernst equation for a single electrode potential is E = E° – \(\frac { RT }{ nF }\) In \(a_{m} n^{4}\)
(iv) The efficiency of a hydrogen oxygen fuel cell is 23%.

Which of the above statement is / are not correct?
(a) (i) & (ii)
(b) (ii) & (iii)
(c) (iv) only
(d) (i) only
Answer:
(c) (iv) only

Question 87.
The specific conductance of 0.1 N KCl solution at 23°C is 0.012 Ohm^-1 cm^-1. The resistance of the cell containing the solution at the same temperature was found to be 55 Ohm. The cell constant will be …………
(a) 0.142 cm^-1
(b) 0.66 cm^-1
(c) 0.9 18 cm^-1
(d) 1.12 cm^-1
Answer:
(c) 0.66 cm^-1
Hint:
k x \(\frac { 1 }{ R }\) x cell constant
Cell constant = k x R
= 0.012 x 55
= 0.66 cm^-1

Question 88.
Which of the following reaction is used to make a fuel cell?
(a) Cd_(s) + 2Ni(OH)_3(s) → CdO_(s) + 2Ni (OH) + H₂O₍₁₎
(b) Pb_(s) + PbO_2(s) + 2H₂SO_4(aq) → 2 PbSO_4(s) + 2H₂O₍₁₎
(c) 2H_2(g) + O_(s) + 2H₂O₍₁₎
(d) 2Fe_(s) + O_2(g) + 4H⁺_(ag) + 2Fe_4(s) + 2H₂O₍₁₎
Answer:
(c) 2H_2(g) + O_(s) + 2H₂O₍₁₎

When lead storage battery is charged
(a) PbO₂ is dissolved
(b) PbSO₄ is deposited on lead electrode
(c) PbSO₄ is deposited on lead electrode

Question 89.
Which colourless gas evolves when NH₄CI reacts with Zinc in a dry cell battery?
(a) NH₃
(b) N₂
(c) H₂
(d) Cl₂
Answer:
(c) H₂
Hint: 2NH₄Cl + Zn → 2NH₃ + ZnCl₂ + H₂ ↑

Question 91.
A cell from the following which converts electrical energy into chemical energy?
(b) Electro chemical cell
(d) Lithium – ion battery
(a) dry cell
(c) Electrolytic cell
Answer:

Question 92.
When 9.65 Coulombs of electricity is passed through a solution of silver nitrate (Atomic weight of Ag = 107.85g), the amount of silver deposited is ……………
(a) 10.8 mg
(b) 5.4 mg
(c) 16.2 mg
(d) 21.2 mg
Answer:
(a) 10.8 mg
Hint:
W_Ag = \(\frac{E_{A g} \times Q}{96500}\) = \(\frac{108 \times 9.65}{96500}\)
= 1.08 x 10^-2

Question 93.
What weight of copper will be deposited by passing 2 Faraday’s of electricity through a cupric salt (Atomic weight of Cu = 63.5)
(a) 2.0g
(b) 3.175g
(c) 63.5g
(d) 127.0g
Answer:
(c) 63.5 g
Hint:
Cu²⁺ + 2e^– → Cu
2 Faraday’s will deposit 1g atom of Cu = 63.5 g

Question 94.
In electrolysis of a fused salt, the weight of the deposit on an electrode will not depend on ….
(a) temperature of the bath
(b) current intensity
(c) electro chemical equivalent of ions
(d) time for electrolysis.
Answer:
(a) temperature of the bath

Question 95.
The mass deposited at an electrode is directly proportional to ………..
(a) atomic weight
(b) equivalent weight
(c) molecular weight
(d) atomic number
Answer:
(b) equivalent weight

Question 96.
Which solution will show the highest resistance during the passage of current?
(a) 0.05 N NaCl
(b) 2N NaCI
(c) 0.1N NaCI
(d) 1N NaCI
Answer:
(b) 2N NaCl

Question 97.
In a galvanic cell, the electrons flow from
(a) anode to cathode through the solution
(b) cathode to anode through the solution
(c) anode to cathode through the external circuit
(d) cathode to anode through the external circuit
Answer:
(c) anode to cathode through the external circuit

Question 98.
Rusting of iron is catalysed by which of the following?
(a) Fe
(b) O₂
(c) Zn
(d) H
Answer:
(d) H

Question 99.
The conductivity of strong electrolyte is ………..
(a) increase on dilution slightly
(b) decrease on dilution
(c) does not change with dilution
(d) depend upon density of electrolyte itself
Answer:
(a) increase on dilutions lightly

Question 100.
Which one is not a conductor of electricity?
(a) NaCl_(aqueous)
(b) NaCl_(solid)
(c) NaCl_(molten)
(d) Ag_(metal)
Answer:
(b) NaCl_(solid)
Hint:
In solid state, NaCl does not dissociate into ions so it does not conduct electricity.

Question 101.
The molar conductivity is maximum for the solution of concentration
(a) 0.00 1 m
(b) 0.005 m
(c) 0.002 m
(d) 0.004 m
Answer:
(a) 0.001 m
Hint:
molar conductance α \(\frac{1}{\text { molarity }}\)

Question 102.
Resistance of 0.2 m solution of an electrolyte is 50 Ohm^-1. The specific conductance of the solution is 1.3 Sm^-1. If resistance of 0.4 m solution of the same electrolyte is 260 Ohm^-1, its molar conductivity is ……..
(a) 62.5 Sm² mol^-1
(b) 6250 Sm² mol^-1
(c) 6.25 x 10^-4 Sm² mol^-1
(d) 625 x 10^-4 Sm² mol^-1
Answer:
(c) 6.25 x 10^-4 Sm² mol^-1

Question 103.
Saturated solution of KCI (or) Na₂SO₄ is used to make salt bridge because
(a) velocity of K⁺ is greater than that of Cl^–
(b) velocity of Cl^– is greater than that of K⁺
(c) velocity of both K⁺ and Cl^-1 are nearly the same
(d) KCI is highly soluble in water.
Answer:
(c) velocity of both K⁺ and Cl^– are nearly the same

Question 104.
Which of the following electrolytic solutions has the least specific conductance?
(a) 0.02 N
(b) 0.2 N
(c) 2 N
(d) 0.002 N
Answer:
(d) 0.002 N

Question 105.
An increase in equivalent conductance of a strong electrolyte with dilution is mainly due to ……….
(a) increase in both the number of ions and ionic mobility of ions
(b) increase in number of ions
(c) increase in ionic mobility of ions
(d) 100% ionization of electrolyte at normal dilution
Answer:
(c) increase in ionic mobility of ions

Question 106.
Li occupies higher position in the electrochcmical series of metals as compared to Cu, since
(a) the standard reduction potential of Li⁺/Li is lower than that of Cu²⁺/Cu
(b) the standard reduction potential of Cu²⁺/Cu is lower than that of Li⁺/Li
(c) the standard oxidation potential of Li/Li⁺ is lower than that of Cu/Cu²⁺
(d) Li is smaller in size as compared to Cu.
Answer:
(a) the standard reduction potential of Li⁺/Li is lower than that of Cu²⁺/Cu

Question 107.
The one which decreases with dilution is …………
(a) conductance
(b) specific conductance
(c) equivalent conductance
(d) molar conductance
Answer:
(b) specific conductance

Question 108.
Corrosion of iron is essentially an electrochemical phenomenon where the cell reactions are …………..
(a) Fe is oxidised to Fe²⁺ and dissolved oxygen in water is reduced to OH^–
(b) Fe is oxidised to Fe²⁺ and H₂O is reduced to O₂^2-
(c) Fe is oxidised to Fe²⁺ and H₂O is reduced to O₂^–
(d) Fe is oxidised to Fe²⁺ and H₂O is reduced to O₂
Answer:
(a) Fe is oxidised to Fe²⁺ and dissolved oxygen in water is reduced to OH^-2

Question 109.
A button cell used in watches functions as following.
Zn_(s) + Ag₂O_(s) + H₂O₍₁₎ → 2 Ag_(s) + Zn²⁺_(aq)+ 2OHsup>-_(aq).
If half cell potentials are Zn²⁺_(aq) + 2e^– → Zn_(s)
E° = – O.76V
Ag₂O_(s) + H₂O₍₁₎ +2e^– 2Ag_(s) + 2OH^–_(aq)E⁰ = 0.34V
The cell potential will be ………..
(a) 1.10V
(b) 0.42V
(c) 0.84V
(d) 1.34V
Answer:
(a) 1.10V
Hint:
Cell potential = E_cathode – E_anode
= 0.34 – (- 0.76)
= 0.34 + 0.76
= 1.10V

Question 110.
Among the following cells Leclanche cell
(I) Nickel – cadmium cell
(II) Lead storage battery
(III) and Mercury Cell
(IV) primary cells are
(a) I & II
(b) I & III
(c) II & III
(d) I & IV
Answer:
(d) I & IV

II. Fill in the blanks.

1. ……… is defined as the resistance of an electrolyte confined between two electrodes having unit cross sectional area and separated by a unit distance
2. The reciprocal of the specific resistance is called the and represented by the symbol ………
3. The SI unit of specific conductance is ………
4. The relation between equivalent conductance and the specific conductance is given as ………
5. Conductivity increases with the ……… in viscosity.
6. A°_m values of the weak electrolytes can be determined using ………
7. ……… is a device in which a spontaneous chemical reaction generates an electric current.
8. ……… is a device that converts electrical energy into chemical energy.
9. The salt bridge contains a agar-agar gel mixed with an inert electrolyte such as ………
10. The SI unit of cell potential is ………
11. The reference electrode SHE has emf of exactly ……… volt
12. The value of charge of one electron is equal to ………
13. For a spontaneous cell reaction, the should be ………
14. ……… is a process in which electrical energy is used to cause a non-spontaneous chemical reaction.
15. The negative E° values shows that the reactions are ………
16. ……… is defined as the amount of a substance deposited or liberated at the electrode by a charge of 1 Coulomb.
17. ……… batteries are used in cell phones.
18. ……… cell is used in pacemakers, electronic watches and cameras.
19. ………battery is used in automobiles.
20. Rusting of iron is an ……… process.

Answer:

1. Specific resistance (or) Resistivity
2. Specific conductance, Kappa(k)
3. Sm^-1
4. Λ = \(\frac{\kappa \times 10^{-3}}{N}\)
5. decrease
6. Kohlraush’s law
7. Galvanic (or) Voltaic cell
8. Electrolytic cell
9. KCl (or) Na₂SO₄
10. Volt (V)
11. zero
12. 1.6 x 10^-19C
13. negative
14. Electrolysis
15. non – spontaneous
16. electro chemical equivalent
17. Li-ion
18. Mercury button
19. Lead storage
20. electro chemical

III. Match the following

Question 1.

Answer:
i. c d a b

Question 2.

Answer:
ii. c a d b

Question 3.

Answer:
iii. d c a b

Question 4.

Answer:
iv. c a d b

Question 5.

Answer:
i. b c d a

Question 6.

Answer:
i. c a d b

IV. Assertion and reasons.

Question 1.
Assertion(A): If the temperature of the electrolytic solution increases, conductance also increases.
Reason (R): Increase in temperature increases the kinetic energy of the ions and decreases the attractive force between the oppositely charged ions and hence conductivity increases.
(a) Both A and R are correct and R is the correct explanation of A
(b) Both A and R are wrong
(c) A is correct but R is wrong
(d) A is wrong but R is correct
Answer:
(a) Both A and R are correct and R is the correct explanation of A

Question 2.
Assertion(A): Molar conductance of a solution increases with increase in dilution.
Reason (R): For a strong electrolyte, inter ionic forces of attraction decreases with dilution and so conductivity increases. For a weak electrolyte, degree of dissociation increases with dilution and conductivity increases.
(a) Both A and R are correct and R is the correct explanation of A .
(b) A and R are wrong
(c) A is correct but R is not the explanation of A
(d) A is wrong but R is correct
Answer:
(a) Both A and R are correct and R is the correct explanation of A

Question 3.
Assertion(A): AC current is used in wheatstone bridge arrangement to measure conductivity of ionic solution.
Reason (R): If DC current is used in wheatstone bridge arrangement, it will lead to electrolys is of the solution taken in the cell. So AC current is used to prevent electrolysis.
(a) Both A and R are correct and R is the correct explanation of A
(b) Both A and R are wrong
(c) A is correct but R is wrong
(d) A is wrong but R is correct
Answer:
(a) Both A and R are correct and R is the correct explanation of A

Question 4.
Assertion(A): Strong electrolytes have low molar conductivity at high concentration.
Reason (R): For a strong electrolyte, at high concentration, the number of constituent ions of the electrolyte is high and hence the attractive force between the oppositely charged ions is also high
(a) Both A and R are correct and R is the correct explanation of A
(b) A is correct but R is wrong
(c) A is wrong but R is correct
(d) Both A and R are wrong
Answer:
(a) Both A and R are correct and R is the correct explanation of A

Question 5.
Assertion(A): In Daniel cell, the salt bridge contains an agar-agar gel mixed with an inert electrolyte KCl (or) Na₂SO₄.
Reason (R): The ions of inert electrolyte do not react with other ions present in half cells and they are not either oxidised or reduced at electrodes.
(a) Both A and R are correct
(b) Both A and R are wrong
(c) A is correct but R is wrong
(d) A is wrong but R is correct
Answer:
(a) Both A and R are correct

Question 6.
Assertion(A): Current stops flowing when E_cell = 0
Reason (R): At E_cell = 0, Equilibrium of the cell reaction is attained.
(a) Both A and R are correct
(b) Both A and R are wrong
(c) A is correct but R is wrong
(d) A is wrong but R is correct
Answer:
(a) Both A and R are correct

Question 7.
Assertion(A): Copper Sulphate can be stored in a Zinc vessel.
Reason (R): Zinc is less reactive than Copper.
(a) Both A and R are correct
(b) Both A and R are wrong
(c) A is correct but R is wrong
(d) A is wrong but R is correct
Answer:
(a) Both A and R are correct

Question 7.
Assertion(A): Copper Sulphate can be stored in a Zinc vessel.
Reason (R): Zinc is less reactive than Copper.
(a) Both A and R are correct
(b) Both A and R are wrong
(c) A is correct but R is wrong
(d) A is wrong but R is correct
Answer:
(b) Both A and R are wrong

Question 8.
Assertion(A): As a lead storage battery gets discharged. density of electrolyte present in it decreases.
Reason (R): Lead and Lead dioxide both react with sulphuric acid to form lead sulphate.
(a) Both A and R are correct
(b) A is correct but R is wrong
(c) A is wrong but R is correct
(d) Both A and R are wrong.
Answer:
(a) Both A and R are correct

Question 9.
Assertion(A): The cell potential of mercury cell is 1.35V which remains constant.
Reason (R): In mercury cell, the electrolyte is a paste of KOH and ZnO.
(a) Both A and R are correct, but R is not the correct explanation of A
(b) Both A and R are correct, but R is the correct explanation of A
(c) A is wrong but R is correct
(d) A is correct but R is wrong
Answer:
(a) Both A and R are correct, but R is not the correct explanation of A

Question 10.
Assertion(A): If an iron rod is dipped in CuSO₄ solution, then blue colour of the solution turns red.
Reason (R): Iron is more reactive than copper and so iron displaces copper from CuSO₄ solution.
(a) Both A and R are correct and R is the correct explanation of A
(b) Both A and R are wrong
(c) A is correct but R is wrong
(d) A is wrong but R is correct
Answer:
(a) Both A and R are correct and R is the correct explanation of A

V. Find the odd one out and give the reasons.

Question 1.
(a) I α V
(b) I = \(\frac { V }{ R }\)
(c) V = IR
(d) R = \(\frac { I }{ V }\)
Answer:
(d) R is the odd one, and other three represents Ohm’s law

Question 2.
(a) m = Zit
(b) Z = \(\frac { m }{ It }\)
(c) m α It
(c) \(\frac{\mathrm{m}_{1}}{\mathrm{Z}_{1}}$\) = \($\frac{\mathrm{m}_{2}}{\mathrm{Z}_{2}}\)
Answer:
(d) \(\frac{\mathrm{m}_{1}}{\mathrm{Z}_{1}}$\) = \($\frac{\mathrm{m}_{2}}{\mathrm{Z}_{2}}\) = is the odd one, all the others are Faraday’s I law but (ci) is Faraday’s ¡I law

Question 3.
(a) Pacemaker
(b) electronic watches
(c) trains
(d) cameras
Answer:
(c) train, Lead storage battery is used in trains, but in all others mercury button cell is used up.

Question 4.
(a) Automobiles
(b) Pacemaker
(c) Train
(d) Inverters
Answer:
(b) Pacemaker. In pacemaker mercury button cell is used whereas in other three, lead storage battery is used up.

Question 5.
(a) Cellular phone
(b) Laptop
(c) Digital Camera
(d) Electronic watch
Answer:
(d) Electronic watch. ¡n this mercury button cell is used whereas in others Li-ion battery is used up.

Samacheer Kalvi 12th Chemistry Electro Chemistry 2 Mark Questions and Answers

VI. Answer the following.

Question 1.
State Ohm’s law.
Answer:
At a constant temperature, the current flowing through the cell (I) is directly proportional to the voltage across the cell (V).
I α V(or) I = \(\frac { V }{ R }\)
V = IR

Question 2.
Define Resistivity. Give its unit.
p (rho) is called the specific resistance (or) resistivity and it is defined as the resistance of an electrolyte confined between two electrodes having unit cross sectional area and are separated by a unit distance. Unit of resistivity is Ohm metre (Ω m)

Question 3.
Define conductance and give its unit.
Answer:
The reciprocal of the resistance \((\frac { 1 }{ 2 })\) is known as the conductance of an electrolytic solution.
The SI unit of conductance is Ohm^-1 (or) Siemen (S)

Question 4.
Define specific conductance. Give its SI unit.
Answer:
The specific conductance is defined as the conductance of a cube of an electrolytic solution of unit dimensions. The SI unit of specific
k = C . \(\frac { l }{ A }\)
conductance is Sm^-1

Question 5.
What Is meant by resistance? Give its unit.
Answer:
Resistance is the opposition that a cell offers to the flow of electric current through it.
R α \(\frac { l }{ A }\)
The SI unit of R = Ohm (Ω)

Question 6.
What is molar conductance? Give its SI unit.
Answer:
The conductance of a conductivity cell in which the electrodes are separated by 1m and having V m³ of electrolytic solution that contains 1 moIe of an electrolyte is known as molar conductance.
Λ_m = k x V
The SI unit of Λ_m = S m² mol^-1

Question 7.
Define equivalent conductance. Give its SI unit.
Answer:
Equivalent conductance is defined as the conductance of ‘V’ m³ of electrolytic solution containing one gram equivalent of electrolyte in a conductivity cell in which the electrodes are one metre apart.
Λ = \(\frac{\kappa \times 10^{-3}}{N}\)
The SI unit of A = S m² gm equivalent’

Question 8.
What are electro chemical cells? Mention its types.
Answer:
Electro chemical cell is a device which inter converts chemical energy into electrical energy and vice versa. It consists of two separate electrodes which are in contact with an electrolyte solution. Electro chemical cells are classified into two types.

1. Galvanic cell and
2. Electrolytic cell.

Question 9.
Distinguish between galvanic cell and electrolytic cell.
Answer:
Galvanic Cell

1. It is a device in which a spontaneous chemical reaction generates an electric current.
2. It converts chemical energy into electrical energy. It is commonly known as Battery.
3. e.g., Daniel cell, Dry cell.
4. A salt bridge is used in this.

Electrolytic cell

1. It is a device in which an electric current from an external source drives a non spontaneous reaction
2. It converts electrical energy into chemical energy.
3. e.g., Electrolysis of molten NaCI.
4. Na salt bridge is used.

Question 10.
What is meant by Faraday? How is it calculated?
Answer:
One Faraday is defined as the charge of one mole of electron.
Charge of one electron = 1.6 x 10^-19C
Charge of 1 mole of electrons = 6.023 x 10²³ x 1.602 x 10^-19C
= 6.023 x 10²³ x 1.602 x 10^-19C
= 96488 C
i.e., IF ≃ 965O0C

Question 11.
Define corrosion. Give one example.
Answer:
The redox process which causes the deterioration of metal is called corrosion. Rusting of iron is an example of corrosion. It is an electro chemical process.

Question 12.
Can you store copper sulphate solution in a zinc pot?
Answer:
Zinc is more reactive than copper. Hence, it displaces copper from copper sulphate solution as follows
Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu (s) So, we cannot store copper sulphate solution in a zinc pot.

Question 13.
Why does the conductivity of a solution decrease with dilution?
Answer:
Conductivity of a solution is the conductance of ions present in a unit volume of solution. On dilution the number of ions per unit volume decreases. Hence, the conductivity decrease.

Question 14.
Suggest a way to determine 10m value of water.

We find out

Then

Question 15.
Write the chemistry of recharging the lead storage battery, highlighting all the materials that are involved during recharging? .
A lead storage battery consists of anode made up of lead, cathode made up of grid of lead packed with lead dioxide (PbO₂) and 38% solution of sulphuric acid is used as an electrolyte. When the battery is in use, the following reaction take place:
Anode: Pb(s) + SO₄^2-(aq) → PbSO₄(s) + 2e^–
Cathode: PbO₂(s) + SO₄^2-(aq) + 4H⁺(aq) + 2e^– → 2PbSO₄(s) + 2H₂O(1)
On charging the battery, the reverse reaction takes place, i.e. PbSO₄ deposited on the electrode is converted back into Pb and PbO₂ and H₂SO₄ regenerated.

Question 16.
What is meant by cell constant?
Answer:
Cell constant is the ratio of the distance between the electrodes (l) and the area of cross-section (A). It is denoted by 1. Its unit is cm^-1. Its SI unit is m^-1.

Question 17.
State two advantages of H₂ – O₂ fuel cell over ordinary cells.
Answer:

1. It is highly efficient.
2. It is pollution free

Question 18.
Why Om for CH₃COOH cannot be determined experimentally?
Answer:
Molar conductivity of weak electrolytes keeps on increasing with dilution and does not become constant even at very large dilution.

Question 19.
Which will have greater molar conductivity and why?
Answer:
Sol. (A) 1 mol KCI dissolved in 200 cc of the solution.
Sol. (B) 1 mol KCI dissolved in 500 cc of the solution.
Sol. (B) will have greater molar conductivity because
λ_m = k x V
with dilution K decreases but V increases, so that product will increase more.

Question 20.
Raju and his father were going in a boat in the river. Raju’s father was going to throw away the cell used in watches and hearing aids into the water. Raju prevented him doing so.

1. As a student of chemistry, why would you advise Raju’s father not to throw the cell in the water body?
2. What is the value associated with the above decision?

Answer:

1. The watch cells are made up of mercury. This mercury will pollute the water. Water contaminated with mercury leads to accumulation of mercury in the body of fishes and other aquatic life.
2. It helps in keeping the environment safe from pollution due to mercury.

Samacheer Kalvi 12th Chemistry Electro Chemistry 3 Mark Questions And Questions

VII.Answer the following questions.

Question 1.
Explain about conductivity cell with an example.
Answer:
1. Sodium chloride (or) potassium chloride is dissolved in a solvent like water, the electrolyte is completely dissociated to give its constituent ions (cations and anions).

2. When an electric field is applied to such an electrolytic solution, the ions present in the solution carry charge from one electrode to another. PLattnium electrode and thereby they conduct electricity. electrode

3. The conductivity of the electrolytic solution is measured using a conductivity cell, solution

Question 2.
Explain about the factors affecting electrolytic conductance. Conductivily Cell
Answer:

1. If the interionic attraction between the oppositely charged ions ofsolute increases, the conductance will decrease.
2. Solvent of high dielectric constant show high conductance in solution.
3. Conductance is inversely proportional to the viscosity of the medium. i.e., conductivity increases with the decrease in viscosity.
4. If the temperature of the electrolytic solution increases, conductance also increases.
5. Molar conductance of a solution increases with increase in dilution. This is because, for a strong electrolyte, inter ionic force of attraction decrease with dilution.
6. For a weak electrolyte, degree of dissociation increases with dilution.

Question 3.
Explain about the variation of molar conductivity with concentration by Kohiraush studies?
Answer:
Kohiraush observed that, increase of molar conductance of an electrolytic solution with the increase in dilution. He deduced the following empirical relationship between the molar conductance (Λ_m) and concentration of the
Λ_m = Λ⁰_m – k\(\sqrt { c }\)
For strong electrolytes such as KCl, NaCl the plot Λ_mV_s\(\sqrt { c }\), gives a straight line. It is also observed that the plot is not a linear one for weak electrolyte.

Question 4.
For strong electrolytes the molar conductivity increases on dilution and reaches a maximum value at infinite dilution. Justify this statement.
Answer:
For a strong electrolyte, at high concentration, the number of constituent ions of the electrolyte in a given volume is high and hence the attractive force between the oppositely charged ions is also high. The ions also experienced a viscous drag due to greater solvation. These factors attribute for the low molar conductivity at high concentration.

When the dilution increases, the ions are far apart and the attractive forces decreases. At infinite dilution, the ions are so far apart, the interaction between them becomes insignificant and hence the molar conductivity increases and reaches a maximum value at infinite dilution.

Question 5.
For weak electrolyte, sudden increase In molar conductance with dilution. Prove this statement.
Answer:
For a weak electrolyte, at high concentration the plot is almost parallel to concentration axis with slight increase in conductivity as the dilution increases. When the concentration approaches zero, there is a sudden increase in the molar conductance and the curve is almost parallel to Am axis. This is due to the fact that the dissociation of the weak electrolyte increases with the increase in dilution (Ostwald’s dilution law).

Question 6.
Explain about Debye-Huckel and Onsagar equation.
Answer:
The influence of ion-ion interactions on the conductivity of strong electrolytes was studied by Debye and Huckel.
They considered that each ion is surrounded by an ionic atmosphere of opposite sign, and derived an expression relating the molar conductance of strong electrolytes with the concentration by It was further developed by Onsagar. For a uni – univalent electrolyte the Debye Huckel and Onsagar equation is given below.
Λ_m = Λ°_m (A + B Λ°m) \(\sqrt { c }\)
Where A and B are constants which depend only in the nature of the solvent and temperature.

Question 7.
What are the values of A and B in Debye Huckel and Onsagar equation?
Answer:
Debye Huckel and Onsagar equation is
Λ_m = Λ°_m (A + B Λ°m) \(\sqrt { c }\)
Where
\(\mathrm{A}=\frac{82.4}{\sqrt{\mathrm{DT}} \mathrm{n}}\)
\(B=\frac{8.20 \times 10^{5}}{3 \sqrt{D T}}\)
D = Dielectric constant of the medium
η = Viscosity of the medium
T = Temperature in Kelvin

Question 8.
How will you calculate degree of dissociation of weak electrolytes and dissociation constant using Kohlrausch’s law?
Answer:
1. The degree of dissociation of weak electrolyte can be calculated from the molar conductivity at a given concentration and the molar conductivity in infinite dilution using the formula

2. According to Ostwald’s dilution law K_a = \(\frac{\alpha^{2} C}{1-\alpha}\)
Substituting a value in the above equation

Question 9.
How would you calculate the solubility of sparingly soluble salt using Kohlrausch’s law?
Answer:
1. Substances like AgCl, PbSO₄ are sparingly soluble in water. The solubility product can be determined using conductivity experiments.

2. Let us consider AgCl as an example
AgCI_(s) → Ag⁺ + Cl^–
K_sp = [Ag⁺] [Cl^–]

3. Let the concentration of [Ag⁺] be ‘C’ mol L^-1.
If [Ag⁺] = C, then [Cl^–] is also equal to C mol L^-1.
K_sp = C.C
K_sp = C².

4. The relationship between molar conductance and equivalent conductance is

Substitute the concentration value in the relation K_sp = C²

Question 10.
What is the relationship between molar mass and electro chemical equivalent. Derive the equation.
Answer:
1. Consider the following general electro chemical redox reaction
Mⁿ⁺(aq) + ne^– → M_(s)

2. We can infer from the above equation that ‘n’ moles of electrons are required to precipitate

3. The quantity of charge required to precipitate 1 mole of Mⁿ⁺ = Charge of ‘n’ moles of electrons = nF

4. In other words, the mass of the substance deposited by one coulomb of charge. Molar mass (M)
Electro chemical equivalent Mⁿ⁺ = \(\frac{\text { Molar mass }(\mathrm{M})}{\mathrm{n}(96500)}\)
(or)
Z = \(\frac{\text { Equivalent mass }}{96500}\)

Question 11.
What is meant by standard reduction potential? What is its application?
Answer:
1. The standard reduction potential (E°) is a measure of the oxidising tendency of the species.
2. The greater the E° value means greater is the tendency shown by the species to accept electrons and undergo reduction.
3. So higher the E° values, lesser is the tendency to undergo corrosion.

Question 12.
What is meant by Electro chemical series? Mention the top most and the least placed element in that series.
Answer:
1. The standard aqueous electrode potential at 298 K for various metal-metal ion electrodes are arranged in the decreasing order of their standard reduction potential values is known as electro chemical series.

2. The strongest reducing agent is Li which has E° value as – 3.05 and it is in bottom of the series.

3. The strongest oxidising agent is F which has E° value as + 2.87 is the first element in that series.

Question 13.
Calculate the emf of the cell in which the following reaction takes place
Ni(s) + 2Ag⁺(0.002 M) —‘ Ni²⁺(0.160 M) + 2 Ag(s)
Given that E°_cell = 1.05 V
Answer:
Applying Nernst equation to the given cell reaction:

= 1.05 – 0.14 V = 0.91 V

Question 14.
If a current of 0.5 ampere flows through a metallic wire for 2 hours, then how many electrons would flow through the wire?
Answer:
Q (coulomb) = 1 (ampere) x t(sec)
= 0.5 ampere x 2 x 60 x 60 = 3600C
A flow of IF, i.e., 96500 C is equivalent to the flow of 1 mole of electrons
i.e., 6.023 x 10²³electrons
3600 C is equivalent to flow of electrons
= \(\frac{6.02 \times 10^{23}}{96500}\) x 3600 2.246 x 10²² electrons,

Question 15.
What are fuel cells? Write the electrode reactions of a fuel cell which uses the reaction of hydrogen with oxygen?
Answer:
A fuel cell is similar to a galvanic cell, it generates electricity directly by the electrochemical conversion of gaseous or liquid fuels fed into the cell as required.
At anode: H₂(g) + 2OH^–(aq) → 2H₂O(l) + 2e^–
At cathode: O₂(g) + 2H₂O(1) + 4e^– → 4OH_–(aq)
Overall reaction : 2H₂(g) + O₂(g) → 2H₂O(l)

Question 16.
Write the cell reaction which occur ¡n the lead storage battery

1. When the battery is in use,
2. When the battery is charging.

Answer:
1. Pb(s) + PbO₂(s) + 2H₂SO₄(aq) → 2PbSO₄(s) + 2H₂O(1)
At anode: Pb(s) + SO^2-₄ → PbSO₄(s) + 2e^–
At cathod: PbO₄(s) + SO^2-₄(aq) + 4H⁺(aq) + 2e^– → PbSO₄(s) + 2H₂O(1)

2. 2PbSO₄(s) + 2H₂O(s) → PbSO₄(s) + 2H₂SO₄(aq)

Question 17.
Describe the composition of anode and cathode in a mercury cell. Write the electrode reactions for this cell.
Answer:
Mercury cell: It consists of zinc mercury amalgam as anode, a paste of HgO and Carbon black is used as cathode. The electrolyte is a paste of KOll and ZnO.
At anode: Zn (amalgam) + 2OH^– → ZnO(s) + H₂O(l) + 2e^–
At cathode: HgO(s) + H₂O + 2e^– → Hg(1) + 2OH^–
The net reaction : Zn (amalgam) + HgO(s) → ZnO(s) + Hg(l)

Question 18.
How much copper is deposited on the cathode of an electrolytic cell If a current of 5 ampere is passed through a solution of copper sulphate for 45 minutes?
Answer:
[Molar mass of Cu = 63.5 g mol^-1, IF = 96,500 C mol^-1]
Cu²⁺(aq) + 2e^– → Cu(s)
m = Z xI x t
= \(\frac{63.5}{2 \times 96500}\) x 5amp x 45 x 60 = \(\frac { 857250 }{ 193000 }\) = 4.44g

Question 19.
How much time would it take in minutes to deposit 1.18 g of metallic copper on a metal object when a current of 2.0 A is passed through the electrolytic cell containing Cu²⁺ ions?
Answer:
[Molar mass of Cu = 63.5 g mol^-1, IF = 96,500 C mol^-1]
m = Z x I x t
1.18 = \(\frac{63.5}{2 \times 96500}\)
t = \(\frac{1.18 \times 2 \times 96500}{2 \times 63.5}\)
= 1793.23 sec
= \(\frac { 1793.23 }{ 60 }\) = 29.88 min

Question 20.
What is a salt bridge? What is it used for?
Answer:
A salt bridge is a U – shaped tube containing concentrated solution of an inert electrolyte like KCl, KNO₃, K₂SO₄, etc., or a solidified solution of an electrolyte such as agar-agar and gelatine. It is used,

1. To complete the electrical circuit by allowing ions to flow from one solution to the other without mixing the two solutions.
2. To maintain the electrical neutrality of the solutions in the two half cells.

Question 21.
Calculate emf of the following cell of 25°C.
Answer:
Fe | Fe²⁺(0.001M) || H⁺(0.01M) | H₂(g) (1 bar) pt
E⁰_(Fe²⁺/Fe) = – 0.44V
E⁰_(H⁺/H2) = 0.00V
Cell reaction
Fe + 2H⁺ Fe²⁺ + H₂
E⁰_cell = E⁰_cathode – E⁰_anode
E⁰_cell = 0.44 – \(\frac{0.0591}{2}\) 10 g \(\frac{\left[10^{-3}\right]}{\left[10^{-2}\right]^{2}}\)
= 0.44 – \(\frac{0.0591}{2}\) 10g 10
= 0.44 – \(\frac{0.0591}{2}\)
E⁰_cell = 0.4105V

Question 22.
What is corrosion? CO₂ is always present in natural water. Explain its effect (increases, stops or no effect) on rusting of Fe.
Answer:
Corrosion is a process of slowly eating away of the metal due to the attack of atmospheric gases on thc surface of metal resulting into the formation of compounds such as oxides, suiphides, carbonates, suiphates, etc.

Factors affecting corrosion are:

1. Reactivity of metal
2. Presence of impurities
3. Presence of air and moisture
4. Strains in metals
5. Presence of electrolytes

CO₂ increases the rusting of iron because greater the number of W ions, faster the rusting will take place.

Samacheer Kalvi 12th Chemistry Electro Chemistry 5 Marks Question

VIII.Answer the following questions.

Question 1.
How would you measure the conductivity of ionic solutions?
Answer:
1. The conductivity of an electrolytic solution is determined by using a wheatstone bridge arrangement in which one resistance is replaced by a conductivity cell filled with the electrolytic solution of unknown conductivity.

2. In the measurement of specific resistance of a metallic wire, a DC power supply is used. Here AC is used for this measurement to prevent electrolysis. Because DC current through the conductivity cell leads to the electrolysis of the solution taken in the cell.

3. A wheatstone bridge is constituted using known resistances P,Q, a variable resistance S and conductivity cell. An AC source (550 Hz to 5 KHz) is connected between the junctions A and C. A suitable detector is connected between the junctions B and D.

4. The variable resistance S is adjusted until the bridge is balanced and in this canditions, there is no current flow through the detector.

5. Under balanced condition
P/Q = R/S
R = P/Q x S ………..(1)
The resistance of the electrolytic solution (R) is calculated from the known resistance values P, Q and the measured S value using the equation (1).

6. Specific conductance (or) conductivity of an electrolyte can be calculated from the resistance value (R) using the following expression

7. The value of cell constant is usually provided by the cell manufacturer. Alternatively the cell constant may be determined using KCI solution whose concentration and specific conductance are known.

Question 2.
Explain about SHE (Standard Hydrogen Electrode).
Answer:
1. It is impossible to measure the emf of a single electrode, but we can H₂ out H₂ measure the potential difference between two electrodes (E_cell) using a voltmeter.

2. To calculate the emf of a single electrode, we need a reference electrode whose emf is known. For that purpose, Standard Hydrogen
Electrode (SHE) is used as the reference electrode.

3. SHE has been assigned an orbitary emf of exactly zero volt.

4. It consists of platinum electrode in contact with 1M HC1 solution and 1 atm hydrogen gas.

5. The hydrogen gas bubbled through the solution at 25°C. SHE can act as cathode as well as an anode.

6. The Half cell reactions are given below:
If SHE is used as a cathode, the reduction reaction is
2H² + 2e^– + H_{2(g,1 atm)} E°= 0 volt
If SHE is used as an anode, the oxidation reaction is
H_{2(g, 1 atm)} 2H⁺_{( aq, 1M)} + 2e^– E° = 0 volt.

Question 3.
How would you determine the reduction potential of Zn/Zn²⁺(aq)? (or) How will you calculate the reduction potential of Half cell?
Answer:
1. Consider the zinc electrode dipped in zinc sulphate solution using SHE

2. Step 1:
The following galvanic cell is constructed using SHE
Zn_(s) | Zn²⁺_(aq.1M) | H_2(g.1atm) | Pt_(s)

3. Step 2:
The emf of the above galvanic cell is measured using a voltmeter. In this case the measured emf of the above galvanic cell is 0.76 V

4. Calculation:
We know that.
E°_cell = (E°_ox)_zn|zn²⁺ + (E°_red)_SHE
E°_cell = 0.76 + 0V
= 0.76 V
This oxidation potential corresponds to the below mentioned half cell reaction which takes place at the cathode
Zn → Zn²⁺ + 2e^– (oxidation)
(y) The emf of the reverse reaction will give the reduction potential
Zn²⁺ + 2e^– → Zn
(E°_red)_zn²⁺|zn = – 0.76V

Question 4.
Derive the relationship between Gibb’s free energy and maximum work obtained from galvanic cell and equilibrium constant.
Answer:
1. In a galvanic cell, chemical energy is converted into electrical energy. The electrical energy produced by the cell is equal to the product of the total charge of the electrons and emf of the cell which drives these electrons between the electrodes.

2. If ‘n’ is the number of moles of electrons exchanged between the oxidising and reducing
agent in the overall cell reaction, then the electrical energy produced by the cell is given
as below.
Electrical energy = change of ‘n’ moles of electrons x E_cell ……………..(1)
Charge of I mole of electrons = one Faraday = 1F
Charge of n moles of electrons = nF ……………..(2)

3. Electrical energy = nFE_cell …………….(3)
This energy is used to do electric work. Therefore the maximum work that can be obtained from a galvanic cell is
Here the – ve sign is introduced to indicate that work is done by the system on the surroundings.

4. Second law of thermodynamics states that the maximum work done by the system is equal to the change in Gibbs free energy of the system
W_max = ΔG …………..(5)

5. ΔG = – nFE_cell (6)
For a spontaneous cell reactions, the AG should be negative. The above expression indicates that E_cell should be positive to get a negative AG value.

6. When all the cell components are in their standard state, the equation (6) becomes
ΔG° = – nFE°_cell …………….(7)

7. The standard free energy change is related to the equilibrium constant as per the following equation.
ΔG° = – RT In K_eq …………..(8)
Comparing equations (7) and (8)
nFE°_cell = RT In K_eq …………..(9)
nFE°_cell = \(\frac { 2.303RT }{ nF }\) log K_eq ………………(10)

Question 5.
Describe about the working principle of Leclanche cell.
Answer:

1. Leclanche cell:
Anode: Zinc container
Cathode: Graphite rod in contact with MnO₂
Electrolyte: Ammonium chloride and Zinc chloride in water.
emf of the cell = 1.5 V

2. Cell reaction:
Oxidation at anode
Zn_(s) → Zn²⁺_(aq) + 2e_– ……………(1)
Reduction at cathode
2NH⁺_{4 (aq)} + 2e^– → 2NH_3(aq) + H_2(aq)

3. The hydrogen gas is oxidised to water by MnO₂
H_2(g)+ 2MnO_2(s) → Mn₂O_3(s) + H₂O₍₁₎ ……(3)
Adding equations 1,2,3 the overall redox reaction
Zn_(s) + 2NH⁺_4(aq) + 2MnO_2(s) → Zn²⁺_(aq) + Mn₂O_3(s) + H₂O₍₁₎ + 2NH₃ …………….(4)

4. The ammonia produced at the cathode combines with Zn²⁺ to form a complex ion [Zn (NH₃)₄]₂₊(aq). As the reaction proceeds, the concentration of NH₄⁺ will decrease and the aqueous NH₃ will increase which lead to the decrease in the emf of the cell.

Question 6.
Explain about the construction and uses of mercury button cell.
Answer:
1. Mercury button cell:
Anode: Zinc Amalgamated with mercury
Cathode: HgO mixed with graphite
Electrolyte: Paste of KOH and ZnO.

2. Oxidation occurs at anode:

3. Reduction occurs at cathode

Hg_(s) + 2OH^–_(aq)
Overall reaction is
Zn_(s) + HgO_(s) → ZnO_(s) + Hg₍₁₎

4. Cell emf: about 1.35 V

5. Uses:
It has higher capacity and longer life. It is used in pacemakers, electronic watches, cameras.

Question 7.
Describe about lead storage battery construction and its uses.
Answer:
Lead storage battery:
1. Anode – Spongy lead
Cathode – Lead plate bearing PbO₂
Electrolyte – 38% by mass of H₂SO₄ with density 1.2 g/ml

2. Oxidation occurs at the anode
Pb_(s) → Pb²⁺_(aq) + 2e^– ………..(1)
The Pb²⁺ ions combine with SO₄^2- to form PbSO₄ precipitate
Pb²⁺_(aq) + SO₄^2- → PbSO_4(s)         …………(2)

3. Reduction occurs at the cathode
PbO_2(s) + 4H⁺_(aq) + 2e^– → + 2H₂O₍₁₎     ……….(3)
The Pb²⁺ ions also combines with SO₄^2- ions to form sulphuric acid to form PbSO₄ Precipitate
Pb²⁺_(aq) + SO^2-₂₊ → PbSO         ………….(4)

4. The overall reaction is,
(1) + (2) + (3) + (4)
Pb_(s) + pbO_2(s) + 4H⁺_(s) + 2SO^2-_4(s) → 2PbSO_4(s) + 2H₂O₍₁₎

5. The emf of a single cell is about 2V. Usually six such cells are combined in series to produce 12 volts.

6. The emf of the cell depends on the concentration of H₂SO₄. As the cell reaction uses SO₄^2- ions, the concentration H₂SO₄ decreases. When the cell potential falls to about 1.8V, the cell has to be recharged.

7. Recharge of the cell – During recharge process, the role of anode and cathode is reversed and H₂SO₄ is regenerated. Oxidation occurs at cathode (now anode)

Reduction occurs at anode (now cathode)
PbSO₄(s) + 2e^– → Pb_(s) + SO^2-_4(sq)
Overall reaction
2 pbSO_4(s) + 2H₂O₍₁₎ → pb_(s) + pbO₂(s) + 4H⁺_(aq) + 2SO^2-_4(aq)
The above reaction is exactly the reverse of redox reaction which takes place while discharging.

8. Uses: Lead storage battery is used in automobiles, trains, inverters.

Question 8.
Describe about lithium-ion battery and its uses.
Answer:
1. Lithium-ion battery
Anode – Porous graphite
Cathode – Transition metal oxide as CoO₂
Electrolyte – Lithium salt in an organic solvent

2. At the anode oxidation occurs
Li_(s) → Li⁺_(aq) + e^–
At the cathode reduction Occurs.
Li⁺ + CoO_2(s) + e^– → Li CoO_2(s)

3. Overall reactions
Li_(s) + CoO₂ → Li CoO_2(s)

4. Both electrodes allow Li ions to move in and out of their structures. During discharge the Li ions produced at the anode moves towards cathode through the non-aquaeous electrolyte.

5. When a potential greater than the emf produced by the cell is applied across the electrode, the cell reaction is reversed and now the Li⁺ ions move from cathode to anode where they become embedded on the porous electrode. This is known as intercalation.

6. Uses: This Li-ion battery is used in cellular phones, Laptop computer and digital camera.

Question 9.
What is corrosion? Explain about the electrochemical mechanism of corrosion.
Answer:
1. The metal is oxidised by oxygen in the presence of moisture. The redox process which causes the deterioration of metal is called corrosion.

2. Corrosion of iron is known as Rusting and it is an electrochemical process.

3. Electrochernical mechanism of corrosion – The formation of rust requires both oxygen and water. Since it is an electrochemical redox process, it requires both an anode and cathode in different places on the iron. The iron surface and a droplet of water on the surface form a tiny galvanic cell.

The region enclosed by water is exposed to low amount of oxygen and it act as anode. The remaining area has high amount of oxygen and it act as cathode. So based on oxygen amount, an electrochem leal cell is formed.
Fe_(s) → Fe²⁺_(aq) + 2e^–
O_2(g) + 4H⁺_(aq) + 4e^– → 2H₂O₍₁₎

4. At anode:
2Fe_(s) → 2Fe²⁺_(aq) + 4e^– E° = 1.23V
The electrons move through the iron metal from the anode to the cathode area where the oxygen dissolved in water is reduced to water.

5. At cathode:
The reaction of atmospheric carbondioxide with water gives carbonic acid which furnishes the H⁺ ions for reduction.
O_2(s) + 4H⁺_(g) + 4H⁺_(aq) → 2H₂O₍₁₎
E° = 1.23 V
= + 1.67V

6. The electrical circuit is completed by the migration of ions through water droplet. The overall redox reaction is
2Fe_(s) + O_2(g) + 4H⁺_(aq) → 2Fe³⁺_(aq) + 2H₂O(1).
E°= 0.44+ 1.23
= + 1.67 V

7. The positive emf value indicates that the reaction is spontaneous.

8. The Fe²⁺ ions are further oxidised to Fe³⁺ which on further reaction with oxygen to form rust.

Question 10.
Explain about the various protection methods to prevent corrosion.
1. Coating metal surface by paint

2. Galvanizing – By Coating with another metal such as zinc. Zinc is stronger oxidising agent than iron and hence it can be more easily corroded than iron. i.e., instead of iron, zinc is oxidised.

3. Cathodic protection: In this technique, unlike galvanizing, the entire surface of the metal to be protected need not be covered with a protecting metal instead, metals such as Mg (or) Zn which is corroded more easily than iron can be used as sacrificial anode and the iron material act as cathode. So iron protected but Mg or Zn gets corroded.

4. Passivation – The metal is treated with strong oxidising agent such as Conc. HNO₃. As a result, a protective layer is formed on the surface of the metal.

5. Alloy formation – The oxidising tendency of iron can be reduced by forming its alloy with other more anodic metals. Example – Stainless steel, an alloy of Fe and Cr.

Question 11.
(a) Give reasons for the following

• Rusting of iron is quicker in saline water than in ordinary water.
• Aluminium metal cannot be produced by the electrolysis of aqueous solution of aluminium salt.

(b) Resistance of a conductivity cell filled with 0.1 M KCI solution is 1oo ohms. If the resistance of the sanie cell when filled with 0.02 M KCI solution is 520 ohms, calculate the conductivity and molar conductivity of 0.02 M KCI solution. Conductivity of 0.01 M KCI solution is 1.29 S m^-1.
Answer:
(a)
1. It is because in saline water, there are inore H₄ ions. Greater the number of H₄ ions, quicker the rusting will take place.

2. It is because aluminium metal is more reactive than hydrogen and it will react with H₂O.

(b)
Cell constant = Conductivity (k) x Resistance (R)
= 1.29 S m^-1 x 100Ω
= 1.29 m^-1 = 1.29 cm^-1
λ_m = \(\frac { 100k }{ M }\)
k = \(\frac { 1 }{ R }\) x \(\frac { l }{ A }\)
k = \(\frac { 1 }{ 520Ω }\) x 1.29 cm^-1, where
k = 2.48 x 10^-3S cm^-1
λ_m = \(\frac{100 \times 0.248 \times 10^{-2}}{0.02}\)
= 124 S cm² mol¹

Question 12.
1. State two advantages of H₂ – O₂ fuel cell over ordinary cell.
2. Silver is electron deposited on a metallic vessel of total surface area 900 cm² by passing a current of 0.5 amp for two hours. Calculate the thickness of silver metal deposited. [Given: Density of silver = 10.5 g cm^-3 Atomic mass of silver = 108 u. IF = 96500 C mol^-1].
Answer:
1.

• It is highly efficient and do not produce pollution.
• The H₂O so produced can be used by astronauts for drinking purpose.

2.
m = Z x l x t
m = \(\frac{108}{96500}\) x 0.5 x 2 x 60 x 60
= \(\frac{108 \times 5}{965 \times 10}\) x 2 x 6 x 6 = 4.03g
4.03g = V x d
4.03 g = V x 10.5 g cm^-3
V = Area x thickness
v = 4.03
= 900 cm² x thickness
Thickness = \(\frac{4.03}{10.5}\)
\(\frac{0.338 \mathrm{cm}^{3}}{900 \mathrm{cm}^{2}}\) = 4.26 x 10^-4cm

Question 13.
Distinguish between Leclanche cell and Lead storage battery.
Answer:
Leclanche Cell

1. It is a primary cell
2. It is a non-rechargeable cell
3. Anode : Zinc container
   Cathode : Graphite rod in contact with MnO₂
4. Electrolytes: Ammonium chloride and zinc chloride in water
5. Emf of the cell = 1.5 V

Lead storage battery

1. It is a secondary cell
2. It is rechargeable cell
3. Anode : Spongy lead
   Cathode : Lead plate bearing PbO₂
4. Electrolytes: 38% by mass of H₂SO₄ with density 1.2 g/ml
5. emf of the cell 2 V.

Question 14.
Account for the following

1. Aluminium undergo slow corrosion than iron.
2. H₂ – O₂ fuel cell ¡s more useful than other cells.

Answer:
1. Aluminium, copper, silver also undergo corrosion but at a slower rate than iron. For eg., let us consider the reduction of Aluminium
Al_(s) → Al³⁺_(aq) + 3e^–
Al³⁺ which reacts with oxygen in air to form a protective coating of AI₂O₃. This coating act as a protective film for the inner surface. So further corrosion is prevented.

2. H₂ – O₂ fuel cell is more advanced. Because it is highly efficient. it is pollution free. In this, H₂ – O₂ fuel cell, energy of combustion of fuel is directly converted to electrical energy.

Common Errors

1. Units of electrical quantities may get confused.
2. Writing cell notation may be difficult.

Rectifications

1.Resistance – R ohm (Ω)
Potential difference – V = Volt
Amount of current – 1 = ampere
Specific resistance (ohm m) (Ω m)
Conductivity = Siemen = S
Specific conductance – k = S m^-1
Molar conductance = S m² mol^-1
Equivalent conductance = S m² gram equivalent^-1
Cell constant = m^-1

2. Easy way is (AC)
solid I aqueous solution II aqueous solution I soLid

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Tamilnadu Samacheer Kalvi 12th Chemistry Solutions Chapter 12 Carbonyl Compounds and Carboxylic Acids

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Samacheer Kalvi 12th Chemistry Chapter 12 Carbonyl Compounds and Carboxylic Acids Text Book Evaluation

Samacheer Kalvi 12th Chemistry Carbonyl Compounds and Carboxylic Acids Multiple Choice Questions

Question 1.
The correct structure of the product ‘A’ formed in the reaction


Answer:

Question 2.
The formation of cyanohydrin from acetone is an example of …………..
(a) nucleophilic substitution
(b) electrophilic substitution
(c) electrophilic addition
(d) Nucleophilic addition
Answer:
(d) Nucleophilic addition

Question 3.
Reaction of acetone with one of the following reagents involves nucleophilic addition followed by elimination of water. The reagent is ………….
(a) Grignard reagent
(b) Sn / HCl
(c) hydrazine in presence of slightly acidic solution
(d) hydrocyanic acid
Answer:
(c) hydrazine in presence of slightly acidic solution

Question 4.
In the following reaction,

Product ‘X’ will not give
(a) Tollen’s test
(b) Victor meyer test
(c) Iodoform test
(d) Fehiing solution test
Answer:
(b) Victor meyer test
Hint:

(x) reduces tollens reagent and Fehiing solution aind it also answers iodoform test.

Question 5.
In the following reaction,

(a) Formaldelyde
(b) diacetoneammonia
(c) hexamethylenetetraamlne
(d) oxime
Answer:
(c) hexamethylenetetraamlne
Hint:
X – HCHO
Y – (CH₂)₆ N₄

Question 6.
Predict the product Z in the following series of reactions

i
Answer:

Hint:

Question 7.
Assertion: 2, 2 – dirnethyl propanoic acid does not give HVZ reaction.
Reason: 2 – 2, dimethyl propanoic acid does, not have – a hydrogen atom
(a) if both assertion and reason are true and reason is the correct explanation of assertion.
(b) if both assertion and reason are true but reason is not the correct explanation of assertion.
(c) assertion is true but reason is false
(d) both assertion and reason are false
Answer:
(a) if both assertion and reason are true and reason is the correct explanation of assertion.
Hint:

Question 8.
Which of the following represents the correct order of acidity in the given compounds
(a) FCH₂COOH > CH₃COOH > BrCH₂COOH > CICH₂COOH
(b) FCH₂COOH > CICH₂COOH > BrCH₂COOH > CH₃COOH
(c) CH₃COOH > CICH₂COOH > FCH₂COOH > Br – CH₂COOH
(d) ClCH₂COOH > CH₃COOH > BrCH₂COOH > ICH₂COOH
Hint.
– I effect increases the acidity. If electronegativity is high, – I effect is also high.

Question 9.
Benzoic acid

(a) anilinium chloride
(b) O – nitro aniline
(c) benzene diazonium chloride
(d) m – nitro benzoic acid
Answer:
(c) benzene diazonium chloride
Hint:

Question 10.
Ethanoic acid

2 – bromoethanoic acid. This reaction is called ……………
(a) Finkeistein reaction
(b) Haloform reaction
(c) Hell – Volhard – Zelinsky reaction
(d) none of these
Answer:
(c) Hell – Volhard – Zelinsky reaction

Question 11.

(a) acetylchloride
(b) chioro acetic acid
(c) α – chiorocyano ethanoic acid
(d) none of these
Hint:

Question 12.
Which one of the following reduces tollens reagent ………
(a) formic acid
(b) acetic acid
(c) benzophenone
(d) none of these
Answer:
(a) formic acid
Hint:

Question 13.


Answer:

Hint:

Question 14.
The TUPAC name of
……………………
(a) but – 3 – enoicacid
(b) but 1 – ene – 4 – oicacid
(c) but 2 – ene – 1 – oic acid
(d) but – 3 – ene – 1 – oicacid
Answer:
(a) but – 3 – enoicacid
Hint:

Question 15.
Identify the product formed in the reaction


Answer:

Hint:
Group is reduced to CH₂ – (Wolff – Kishner reduction)

Question 16.
In which case chiral carbon is not generated by reaction with HCN

Answer:

Hint:

Question 17.
Assertion: p – N, N – dimethyl aminobenzaldehyde undergoes benzoin condensation
Reason: The aldehydic (- CHO) group is meta directing
(a) if both assertion and reason are true and reason is the correct explanation of assertion.
(b) if both assertion and reason are true but reason is not the correct explanation of assertion.
(c) assertion is true but reason is false
(d) both assertion and reason are false
Answer:
(b) if both assertion and reason are true but reason is not the correct explanation of assertion.
Hint:

Question 18.
Which one of the following reaction is an example of disproportionation reaction …………….
(a) Aldol condensation
(b) cannizaro reaction
(c) Benzoin condensation
(d) none of these
Answer:
(b) cannizaro reaction
Hint:

Question 19.
Which one of the following undergoes reaction with 50% sodium hydroxide solution to give the corresponding alcohol and acid …………
(a) Phenylmethanal
(b) ethanal
(c) ethanol
(d) methanol
Answer:
(a) Phenylmethanal

Question 20.
The reagent used to distinguish between acetaldehyde and benzaldehyde is ………..
(a) Tollens reagent
(b) Fehling’s solution
(c) 2, 4 – dinitrophenyl hydrazine
(d) semicarbazide
Answer:
(b) Fehling’s solution

Question 21.
Phenyl methanal is reacted with concentrated NaOH to give two products X and Y. X reacts with metallic sodium to liberate hydrogen X and Y are ………….
(a) sodiumbenzoate and phenol
(b) Sodium benzoate and phenyl methanol
(c) phenyl methanol and sodium benzoate
(d) none of these
Answer:
(c) phenyl methanol and sodium benzoate
Hint:

Question 22.
In which of the following reactions new carbon – carbon bond is not formed?
(a) Aldol condensation
(b) Friedel craft reaction
(c) Kolbe’s reaction
(d) Wolf kishner reduction
Answer:
(d) Wolf kishner reduction

Question 23.
An alkene “A” on reaction with O₃ and Zn – H₂O gives propanone and ethanol in equimolar ratio. Addition of HCl to alkene “A” gives “B” as the major product. The structure of product “B” is ……………

Answer:

Hint:

Question 24.
Carboxylic acids have higher boiling points than aldehydes, ketones and even alcohols of comparable molecular mass. It is due to their ………………
(a) more extensive association of carboxylic acid via van der Waals force of attraction
(b) formation of carboxylate ion
(c) formation of intramolecular H – bonding
(d) formation of intermolecular H – bonding
Answer:
(d) formation of intermolecular H – bonding

Question 25.
Of the following, which is the product formed when cyclohexanone undergoes aldol condensation followed by heating?

Answer:

Hint:

II. Answer the following questions.

Question 1.
How is propanoic acid is prepared starting from

1. an alcohol
2. an alkyihalide
3. an alkene

Preparation of propanoic acid from,
Answer:
1. Alcohol:

2. Alkylhalide:

3. Alkene:

Question 2.
A Compound (A) with molecular formula C₂H₃N on acid hydrolysis gives(B) which reacts with thionyichioride to give compound(C). Benzene reacts with compound (C) in presence of anhydrous AlCl₃ to give compound (C). Compound (C) on reduction with gives (D). Identify (A), (B), (C) and D. Write the equations.
Answer:
1. Compound (A) with molecular formula C₂H₃N is methyl cyanide. (CH₃CN)

2. Methyl cyanide (A) on hydrolysis gives acetic acid (B)

3. Acetic acid (B) with thionyl chloride to give acetyl chloride (C)

4. Benzene reacts with acetyl chloride (C) in the presence of anhydrous AlCl₃ to give acetophenone (D)

5. Acetyl chloride (C) on reduced in the presence of Pd / H₂ and Barium sulphate, to gives acetaldehyde (E).

Question 3.
Identify X and Y

Answer:

Question 4.
Identify A, B and C

Answer:

Question 5.
A hydrocarbon A(molecular formula C₈H₁₀) on ozonolysis gives B(C₄H₆O₂ ) only. Compound C( C₃H₅Br) on treatment with magnesium in dry ether gives (D) which on treatment with CO₂ followed by acidification gives (B). Identify A, B, C and D.
Answer:
1. Molecular formula C₈H₁₀ is 1, 2 – dicyclopropylethyne.

2. 1, 2 – dicyclo propyl ethyne (A) on ozonolysis to give cyclo propyl carboxylic acid (B)

3. Compound C₃H₅Br is Bromo cyclo propane (C), which on reacts with Mg in dry ether gives Grignard reagent (D) which on treatment with CO₂ followed by acidification gives cyclo propyl carboxylic acid (B).

Question 6.
Identify A, B, C and D

Answer:

Question 7.
An alkene (A) on ozonolysis gives propanone and aldehyde (E). When (B) is oxidised (C) is obtained. (C) is treated with Br₂ JP gives (D) which on hydrolysis gives (E). When propanone is treated with HCN followed by hydrolysis gives (F). Identify A, B, C, D and E and F.
Answer:
1. 2 – methyl – but – 2 – ene (A) on ozonolysis gives propanone and acetaldehyde (B)

2. Acetaldehyde (B) is oxidised to give acetic acid (C), which on further treated with Br₂ / P give monobromo acetyl bromide (D) which on hydrolysis gives monobromo acetic acid (E).

3. Propanone is treated with HCN followed by hydrolysis to gives 2 – methyl – 2 – hydorxy propanoic acid (F)

Question 8
How will you convert benzaldehyde into the following compounds?

1. benzophenone
2. benzoic acid
3. 2 – hydroxyphenylaceticacid.

Answer:
1. conversion of benzaldehyde into benzophenone.

2. conversion of benzaldehyde into benzoic acid.

3. conversion of benzaldehyde into 2 – hydroxy phenyl acetic acid.

Question 9.
What is the action of HCN on

1. propanone
2. 2, 4 – dichiorobenzaldehyde.

Answer:
1. Propanone reacts with HCN.

2. 2, 4 – dichlorobenzaldehyde reacts with HCN.

Question 10.
A carbonyl compound A having molecular formula C₅H₁₀O forms crystalline precipitate with sodium bisuiphate and gives positive iodoform test. A does not reduce Fehling solution. Identify A.
Answer:
1.

2. Pentan – 2 – one gives positive iodoform test, but it does not reduce Fehling’s solution.

3. Hence carbonyl compound A having molecular formula C₅H₁₀O is pentan – 2 – one.

Question 11.
Write the structure of the major product of the aldol condensation of benzaldehyde with acetone.
Answer:
Step 1:

Step 2:

Step 3:

Step 4:

Question 12.
How are the following conversions effected

1. propanal into butanone
2. Hex – 3 – yne into hexan – 3 – one.
3. phenylmethanal into benzoic acid
4. phenylmethanal into benzoin

Answer:
1. propanal into butanone

2. Hex – 3 – yne into hexan – 3 – one

3. phenylmethanal into benzoic acid

4. phenylmethanal into benzoin

Question 13.
Complete the following reaction.

Answer:

Overall reaction:

Question 14.
Identify A, B and C

Answer:

Question 15.
When ketones are undergo oxidation, the C – C bond Is cleaved. When a strong oxidising agent is used to oxidise 2, 5 – dimethyl hexan – 3 – one mention the products with their names.
Answer:

Question 16.
How will you convert following conversion?

1. Acetic acid into acetic anhydride
2. Methyl acetate into ethyl acetate
3. Methyl acetate into acetamide
4. Acetyl chloride into acetophenone
5. Sodium acetate into ethane
6. Ethanal into lactic acid
7. Toluene into benzoic acid
8. Benzaldehyde into malachite green
9. Benzaldehyde into Cinnamic acid
10. Ethyne into acetaldehyde

Answer:
1. Conversion of Acetic acid into acetic anhydride

2. Conversion of Methyl cyanate into acetamide.

3. Conversion of Methyl cyanate into acetamide.

4. Conversion of Acetyl chloride into acetophenone.

5. Conversion of Sodium acetate into ethane.

6. Conversion of Ethanal into lactic acid.

7. Conversion of Toluene into benzoic acid.

8. Conversion of Benzaldehyde into malachite green.

9. Conversion of benzaldehyde into cinnamic acid.

10. Conversion of Ethyne into acetaldehyde.

Samacheer Kalvi 12th Chemistry Carbonyl Compounds and Carboxylic Acids Evaluate yoursel

Question 1.
Write the IUPAC name for the following compound.

Answer:

Question 2.
Wrtie all possible structural isomers and position isomers for the ketone represented by the molecular formula C₅H₁₀O.
Answer:
Molecular formula C₅H₁₀O exhibits following possible ketone structural isomers and position isomers.

Question 3.
What happens when the following alkenes are subjected to reductive ozonolysis.

1. propene
2. 1 – Butene
3. Isobutylene

Answer:
1. propene

2. 1 – Butene

3. Isobutylene

Question 4.
What happens when n-propyl benzene is oxidised using H⁺ / KMnO₄?
Answer:
When n – propyl benzene is oxidised with H⁺ / KMnO₄ to gives benzoic acid.

Question 5.
How will you prepare benzoic acid using Crignard reagent.
Answer:
Preparation of benzoic acid using Grignard reagent:

Question 6.
Why acid anhydride are preferred to acyl chloride for carrying out acylation reactions?
Answer:
Acid anhydride are preferred to acyl chloride for carrying out acylation reactions. Because

1. Easily available
2. Cheap
3. Easy to prepare
4. Easily undergo acylation without irritating odours

Samacheer Kalvi 12th Chemistry Carbonyl Compounds and Carboxylic Acids Additional Questions

Samacheer Kalvi 12th Chemistry Carbonyl Compounds and Carboxylic Acids 1 Mark Questions and Answers

I. Choose the best answer.

Question 1.
Which one of the following aldehyde is derived from vitamin B, function as a co – enzyme?
(a) Pyridoxal
(b) Formaldehyde
(c) Ethanal
(d) Propanal
Answer:
(a) Pyridoxal

Question 2.
Which one of the following is used in the manufacture of Bakelite?
(a) Methanal
(b) Ethanal
(c) Phenyl methanal
(d) Butanal
Answer:
(a) Methanal

Question 3.
Which is used as a drug to reduce fever?
(a) Diethyl ether
(b) Acetone
(c) Acetophenone
(d) Paracetamol
Answer:
(d) Paracetamol

Question 4.
The IUPAC name of Acrolein is
(a) Prop – 2 – enal
(b) Propanal
(c) Ethenal
(d) 1 – butanal
Answer:
(a) Prop – 2 – enal

Question 5.
The IUPAC name of crotanaldehyde CH₃ – CH = CH – CHO is …………….
(a) Prop – 2 – enal
(b) But – 2 – enal
(c) Ethenal
(d) Phenyl methanal
Answer:
(b) But – 2 – enal

Question 6.
The IUPAC name of is
…………………..
(a) Glyceraldehyde
(b) Acrolein
(c) 2, 3 – dihydroxy propanal
(d) Butanal
Answer:
(c) 2, 3 – dihydroxy propanal

Question 7.
Which one of the following is called Mesityl oxide?

Answer:

Question 8.
Which one of the following is called 3 – oxopentanal?

Answer:

Question 9.
Which one of the following is names as 3 – methyl cyclopentanone?

Answer:

Question 10.
Which one of the following is the hybridised state of C atoms in carbonyl carbon?
(a) sp
(b) sp³d
(c) sp³
(d) sp²
Answer:
(d) sp²

Question 11.
Which of the following reagent is used to get aldehyde from alcohol by oxidation method?
(a) Na₂Cr₂O₇
(b) KMnO₄
(c) PCC
(d) LiAlH₄
Answer:
(c) PCC

Question 12.
The product formed when but – 2 – ene is on ozonolysis is ………….
(a) Propanone
(b) Methanal
(ç) Ethanal
(d) Butanal
Answer:
(ç) Ethanal

Question 13.
Which one of the following should be ozonolysed to get a mixture of ethanal and propanone?
(a) Propene
(b) But – 2 – ene
(c) Ethylene
(d) 2 – methyl – but – 2 – ene
Answer:
(d) 2 – methyl – but – 2 – ene

Question 14.
The products formed when propene is ozonolysed are …………….
(a) HCHO + CH₃CHO
(b) CH₃CHO
(c) HCOOH + CH₃COOH
(d) CH₃COCH₃
Answer:
(a) HCHO + CH₃CHO

Question 15.
Identify the products formed when But- 1-ene undergoes reductive ozonolysis?
(a) HCHO + CH₃CHO
(b) HCHO + CH₃CH₂CHO
(c) CH₃COCH₃ + CH₃CHO
(d) HCHO + CH₃COCH₃
Answer:
(b) HCHO + CH₃CH₂CHO

Question 16.
Which one of the following should be subjected to reductive ozonolysis to get only formal dehyde?
(a) CH ≡ CH
(b) CH₃ – CH = CH₂
(c) CH₂ = CH₂
(d) CH₃ – CH₃
Answer:
(c) CH₂ = CH₂

Question 17.
What are the products formed when Isobutylene is subjected to ozonolysis?
(a) HCHO + CH₃CHO
(b) CH₃COCH₃ + HCHO
(c) CH₃CHO + CH₃COCH
(d) CH₃COCH₃ + CH₃CH₂CHO
Answer:
(b) CH₃COCH₃ + HCHO

Question 18.
Which one of the following is formed when acetylene is hydrolysed in the presence of HgSO₄ and H₂SO₄?
(a) Ethanal
(b) Ethylene
(c) Ethane
(d) Ethanol
Answer:
(d) Ethanol

Question 19.
Hydrolysis of prop – 1 – yne in the presence of HgSO₄ and H₂SO₄ gives ……………

Answer:

Question 20.

Answer:
(a) CaCO₃ + H₂
(b) CO₂ + H₂O + Ca
(c) HCHO + CaCO₃
(d) CO + H₂O + Ca(OH)₂
Answer:
(c) HCHO + CaCO₃

Question 21.
Calciwn acetate on dry distillation gives …………
(a) Acetic acid
(b) Propanone
(c) Ethanol
(d) Propanal
Answer:
(b) Propanone

Question 22.
Which of the following calcium salts are required to get ethanal by dry distillation process?

Answer:

Question 23.
The conversion of acetyl chloride to acetaldehyde by the action of Pd/BaSO₄ is called ………………..
(a) Perkin’s reaction
(b) Stephens reaction
(c) Clemmenoon reduction
(d) Rosenmund reduction
Answer:
(d) Rosenmund reduction

Question 24.
Which of the following cannot be prepared by Rosenmund reduction method?
(a) Acetaldehyde
(b) Formaldehyde
(c) Ketone
(d) Both b & c
Answer:
(d) Both b & c

Question 25.
In Rosenmunds reduction, the action of BaSO₄ is …………….
(a) Promoter
(b) Catalyst poison
(c) Positive catalyst
(d) Negative catalyst
Answer:
(b) Catalyst poison

Question 26.
Which one of the following is an intermediate product in Stephen’s reaction?
(a) Amines
(b) Amides
(c) Imines
(d) Amino acid
Answer:
(c) Imines

Question 27.
Which one of the following is used as selective reducing agent in the conversion of cyanide to aldehyde?
(a) Raney Ni
(b) LiAlH₄
(c) SnCl₂ / HCl
(d) DIBAL – H
Answer:
(d) DIBAL – H

Question 28.
Identify the product formed when benzaldehyde reacts with chromyl chloride?
(a) Benzoic acid
(b) Benzaldehyde
(c) Phenyl methanol
(d) Phenol
Answer:
(b) Benzaldehyde

Question 29.
The conversion reaction of Benzene to Benzaldehyde is known as ……………..
(a) Rosenmund reduction
(b) Stephen reduction
(c) Gattermann koch reaction
(d) Friedel – crafts reaction
Answer:
(c) Gattermann koch reaction

Question 30.
Which one of the following is used to convert acetyl chloride to acetone?
(a) CdCl₂
(b) CrO₂CI₂
(c) Cu₂CI₂
(d) NaCl
Answer:
(a) CdCl₂

Question 31.
Which one of the following is the best method to prepare alkyl aryl ketone and diaryl ketones?
(a) Stephen reaction
(b) Knoevengal reaction
(c) Ciemmenson reduction
(d) Friedel crafts reaction
Answer:
(d) Friedel crafts reaction

Question 32.
The product formed when Benzoyl chloride reacts with benzene is ………….
(a) Benzyl benzoate
(b) Benzophenone
(c) Benzyl chloride
(d) Benzyl alcohol
Answer:
(b) Benzophenone

Question 33.
Which one of the following is used as catalyst in Friedel Crafts reaction?
(a) Anhydrous ZnCl₂
(b) Anhydrous CuCl₂
(c) Anhydrous AlCl₃
(d) Androus CaCl₂
Answer:
(c) Anhydrous AlCl₃

Question 34.
During nucleophilic addition reaction, the hybridisation of carbon changes from
(a) sp² to sp³
(b) sp³ to sp²
(c) sp to sp³
(d) dsp² to sp³
Answer:
(a) sp² to sp³

Question 35.
Which one of the following is formed as a product when ethanal is treated with 2 equivalent of methanol?
(a) 1, 1 – dimethoxy methane
(b) 1 ,2 – dimethoxy ethane
(c) 1, 1 – dimethoxy ethane
(d) 1, 1 – diethoxy ethane
Answer:
(c) 1, 1 – dimethoxy ethane

Question 36.
Which aldehyde does not give aldimine with etheral ammonia solution?

Answer:

Question 37.
Identify the product formed when acetaldehyde reacts with ammonia?

Answer:

Question 38.
Which one of the following is formed when methanal reacts with ammonia?
(a) Tetramethylene hexamine
(b) Hexamethylene tetramine
(c) Formaldehyde ammonia
(d) Aldimine
Answer:
(b) Hexamethylene tetramine

Question 39.
Which one of the following is used as, an urinary antiseptic?
(a) Urotropine
(b) Urea formaldehyde
(c) Formalin
(d) Aldimm
Answer:
(a) Urotropine

Question 40.
Which one of the reactions gives an explosive RDX?
(a) Nitration of phenol
(b) Nitration of glycol
(c) Nitration of urotropine
(d) Nitration of glycerol
Answer:
(c) Nitration of urotropine

Question 41.
Which one of the following is called hydrobenzamide?

Answer:

Question 42.
Which one of the following is formed when benzaldehyde reacts with ammonia?
(a) Benzalamine
(b) Benzylamine
(c) Hydrobenzarnide
(d) Benzarnide
Answer:
(c) Hydrobenzarnide

Question 43.
Which rule governes the oxidation of unsymmetrical ketone?
(a) Markovnikoff’s rule
(b) Popoff s rule
(c) Antimarkovnikoff s rule
(d) Hund’s rule
Answer:
(b) Popoff s rule

Question 44.
What are the products formed when 2-butanonc is oxidised by conc – HNO₃?

Answer:

Question 45.

In this reaction A and B are …………

Answer:

Question 46.
Name the product formed Acetaldehyde reacts with Zinc amalgam and conc.HCl?
(a) Propane
(b) Ethane
(c) Ethene
(d) Ethanal
Answer:
(b) Ethane

Question 47.
The reagent used in the Conversion of  group into – CH₂ – group is …………..
(a) Zn + Hg / HCl
(b) NH₂ – NH₂ + C₂H₅ONa
(c) mg / Hg / H₂O
(d) either (a) or (b)
Answer:
(d) either (a) or (b)

Question 48.
The product formed when Acetone is subjected to Clemmenson reduction is ……………..
(a) Acetic acid
(b) Propanoic acid
(c) Propane
(d) Propanal
Answer:
(c) Propane

Question 49.
Which one of the following is formed when acetone is treated with magnesium amalgam and water?
(a) Pinacol
(b) Acetyl acetone
(c) Aceto acetic ester
(d) 1 ,2 – dimethyl butane 1, 2 – diol
Answer:
(a) Pinacol

Question 50.
Which one of the following does not undergo halo form reaction?

Answer:

Question 51.
Which one of the following undergoes halo form reaction?
(a) HCHO
(b) C₆H₅CHO
(c) CH₃CHO
(d) CH₃ – CH₂ – CH₂OH
Answer:
(c) CH₃CHO

Question 52.
Which one of the following is formed when acetaldehyde is warmed with dilute NaOH?
(a) But – 2 – enal
(b) Butan – 1 – al
(c) 3 – hydroxy butanal
(d) 2 – hydroxybutanoic acid
Answer:
(c) 3 – hydroxy butanal

Question 53.
The IUPAC naine of Acetaldol is ……………
(a) 3 – hydroxy butanal
(b) Aldol
(c) 2 – hydroxy butanal
(d) Butanal
Answer:
(a) 3 – hydroxy butanal

Question 54.
Which one of the following is formed when benzaldehyde reacts with acetaldehyde?
(a) Cinnamic acid
(b) Cinnamaldehyde
(c) Benzylidene acetone
(d) 3 – hydroxy propanal
Answer:
(b) Cinnamaldehyde

Question 55.
The crossed aldol condensation product of the reaction between Formaldehyde and Acetaldehyde is ………………
(a) 3 – hydroxy propanol
(b) 3 – hydroxy propanal
(c) 2 – hydroxy butanal
(d) 3 – hydroxy butanal
Answer:
(b) 3 – hydroxy propanal

Question 56.
The reaction of benzaldehyde with 50% NaOH is called …………..
(a) Benzoin condensation
(b) Claisen – schmidt reaction
(c) Perkin’s reaction
(d) Cannizaro reaction
Answer:
(d) Cannizaro reaction

Question 57.
The reaction of phenyl methanal and ethanal in the presence of dilute NaOH is known as ……………..
(a) Cannizaro reaction
(b) Aldol condensation
(c) Claisen – schmidt condensation
(d) Perkin’s reaction
Answer:
(c) Claisen – schmidt condensation

Question 58.
What is the second step in Cannizaro reaction mechanism?
(a) Attack of OH^– on carbonyl carbon
(b) Acid base reaction
(c) Protonation of carbonyl oxygen
(d) Hydride ion transfer
Answer:
(d) Hydride ion transfer

Question 59.
The first step take place in Cannizaro reaction mechanism is ……………..
(a) Aftack of OH^– on carbonyl carbon
(b) Protonation of carbonyl oxygen
(c) Acid base reaction
(d) Hydride ion transfer
Answer:
(a) Aftack of OH^– on carbonyl carbon

Question 60.
Which one of the following is formed when benzaldehyde reacts with alcoholic KOH?
(a) Benzyl alcohol
(b) Potassium henzoate
(c) Benzoin
(d) Benzoic acid
Answer:
(c) Benzoin

Question 61.
What is the name of the reaction of alcoholic KOH with Benzaldehyde’?
(a) Cannizaro reaction
(c) Benzoin condensation
(b) Perkin’s reaction
(d) Aldol condensation
Answer:
(c) Benzoin condensation

Question 62.
Which one of the following is formed when benzaldehyde reacts with acetic anhydride?
(a) Cinnamaldehyde + Acetaldehyde
(b) Cinnamic acid + Acetic acid
(c) Benzyl alcohol + Benzoic acid
(d) Benzal aniline + Acetic acid
Answer:
(b) Cinnamic acid + Acetic acid

Question 63.
What is the name of the reaction between Benzaldehyde and acetic anhydride?
(a) Peridn’s reaction
(b) Knoerenagal reaction
(c) Cannizaro reaction
(d) Kolbe’s reaction
Answer:
(a) Peridn’s reaction

Question 64.
What are the reagents required to prepare Benzal aniline (or) Schiff’s base?
(a) Benzyl amine + Ammonia
(b) Benzal amine + Ammonia
(c) Benzaldehyde + Aniline
(d) Phenol + Aniline
Answer:
(c) Benzaldehyde + Aniline

Question 65.
Which one of the following is the formula of Schiff’ s base’?
(a) C₆H₅ – NH NH₂
(b) C₆H₅ CH = N – C₆H₅
(b) Perkin’s reaction
(d) Aldol condensation
Answer:
(b) C₆H₅ CH = N – C₆H₅

Question 66.
Which one of the following is used as a catalyst in Knoevenagal reaction?
(a) Pyrimidine
(b) Pyridine
(c) PCC
(d) CdCl₂
Answer:
(b) Pyridine

Question 67.
Which one is formed when Benzaldehyde reacts with Malonic acid in the presence of Pyridine?
(a) Cinnamaldehyde
(b) Benzoin
(c) Hydrobenzamide
(d) Cinnamic acid
Answer:
(d) Cinnamic acid

Question 68.
Name the product formed when Benzaldehyde reacts with N,N – dimethyl aniline in the presence of conc.H₂SO₄?
(a) Cinnamic acid
(b) Skiffs base
(c) Malachite green dye
(d) p – hydroxy azodye
Answer:
(c) Malachite green dye

Question 69.
Identify the product formed when benzaldehyde reacts with chlorine in the presence of conc.FeCl₃?
(a) m – chlorobenzaldehyde
(b) O – chlorobenzaldehyde
(c) p – chiorobenzaldehyde
(d) Benzoyl chloride
Answer:
(a) m – chlorobenzaldehyde

Question 70.
Identify the product formed when benzaldehyde reacts with chlorine in the absence of catalyst?
(a) p – chiorobenzaldehyde
(b) O – chiorobenzaldehyde
(c) Benzoyl chloride
(d) m – chlorobenzaldehyde
Answer:
(c) Benzoyl chloride

Question 71.
Which one of the following is used to test ketones?
(a) lodoform test
(b) Tollen’s reagent test
(c) Fehling’s solution test
(d) Benedict’s solution test
Answer:
(a) lodoform test

Question 72.
Which one of the following is not used to identify aldehydes?
(a) Benedict’s solution test
(b) Fehling’s solution test
(c) Dye test
(d) Tollen’s reagent test
Answer:
(c) Dye test

Question 73.
What is the colour change take place when Fehling’s solution is added to an aldehyde?
(a) Red to blue
(b) Blue to red
(c) Red to green
(d) Green to blue
Answer:
(b) Blue to red

Question 74.
Which one of the following is used for preserving biological specimens?
(a) Urotropine
(b) Formalin
(c) Schiff’s base
(d) Benzoin
Answer:
(b) Formalin

Question 75.
Which one of the following is formed when phenol is heated with formalin?
(a) Bakelite
(b) PVC
(c) Polyurethane
(d) Polyester
Answer:
(a) Bakelite

Question 76.
RDX is otherwise named as …………….
(a) Cyclonite
(b) Cyclohexane
(c) 1, 4 – dione
(d) Cyclohexanol
Answer:
(a) Cyclonite

Question 77.
Which one of the following is used as a hypnotic?
(a) Acetaldehyde
(b) Formalin
(c) Paraldehyde
(d) Formaldehyde
Answer:
(c) Paraldehyde

Question 78.
Which one of the following is used in silvering of mirrors?
(a) Paraldehyde
(b) Benzaldehyde
(c) Acetone
(d) Acetaldehyde
Answer:
(d) Acetaldehyde

Question 79.
Which one of the following is used in the manufacture of smokeless powder (cordite)?
(a) Acetone
(b) Acetaldehyde
(c) Acetic acid
(d) Formaldehyde
Answer:
(a) Acetone

Question 80.
Which one of the following is used as nail polish remover?
(a) CH₃CHO
(b) HCHO
(c) CH₃COCH₃
(d) C₆H₅COCH₃
Answer:
(c) CH₃COCH₃

Question 81.
Which is used in the manufacture of thermosoftening plastic perspex?
(a) Acetaldehyde
(b) Formaldehyde
(c) Acetone
(d) Acetophenone
Answer:
(c) Acetone

Question 82.
Which of the following is called hyphone?

Answer:

Question 83.
Which of the following is used in the preparation of benzhydrol drop?
(a) Benzaldehyde
(b) Benzophenone
(c) Acetophenone
(d) Benzoin
Answer:
(b) Benzophenone

Question 84.
Consider the following statements.
(i) Terminal olefins gives Formaldehyde as one of the product
(ii) Oxidation of alcohols using pcc yield carboxylic acids
(iii) Catalytic dehydrogenation of alcohols give either aldehyde or ketone.
Which of the above statement is/are not correct?
(a) (ii) only
(b) (i) & (iii)
(c) (ii) & (iii)
(d) (ii) only
Answer:
(a) (ii) only

Question 86.
Consider the following statements:
(i) Formaldehyde is a gas at room temperature and acetaldehyde is a volatile liquid.
(ii) The oxidation of symmetrical ketones is governed by Popoti’s rule.
(iii) Aliphatic aldehyde react with primary amines in the presence of base gives Schiff’s base.
Which of the above statement is/are not correct?
(a) (i) only
(b) (ii) only
(c) (ii) & (iii)
(d) (i) & (ii)
Answer:
(c) (ii) & (iii)

Question 87.
The JUPAC name of is
(a) Benzene carboxylic acid
(b) Benzoic acid
(c) 2 – phenyl ethanoic acid
(d) 2 – phenyl acetic acid
Answer:
(c) 2 – phenyl ethanoic acid

Question 88.
The formula of malonic acid is …………

Answer:

Question 89.
The IUPAC name of HOOC – (CH₂)₄ – COOH is ………………
(a) Adipic acid
(b) Butane dioic acid
(c) Hexane diolc acid
(d) Glutaric acid
Answer:
(c) Hexane diolc acid

Question 90.
Which one of the following is the formula of Succinic acid?
(a) HOOC – CH₂ – COOH
(b) HOOC – (CH₂)₂ – COOH
(c) HOOC – (CH₂)₄ – COOH
(d) HOOC – (CH)₃ – COOH
Answer:
(b) HOOC – (CH₂)₂ – COOH

Question 91.
Consider the following statements.
(i) In – COOH group, the centre carbon atom and both the oxygen atoms are in sp³ hybridisation.
(ii) RCOOH can be represented as a resonance hybrid of two canonical structures.
(iii) Carboxylic carbon is less electrophilic than carbonyl carbon because of the reasonan structure.
Which of the above statement is/are correct?
(a) (iii) only
(b) (ii) only
(c) (i) only
(d) (i) & (ii)
Answer:
(b) (ii) only

Question 92.
Which one of the following reacts with methyl magnesium iodide followed by acid hydrolysis yield acetic acid?
(a) Solid CO₂
(b) HCHO
(c) CH₃CHO
(d) CH₃CN
Answer:
(a) Solid CO₂

Question 93.
Which one of the following acid cannot be prepared from grignaid reagent by the action of dry ice?
(a) CH₃COOH
(b) C₆H₅COOH
(c) CH₃ – CH₂COOH
(d) HCOOH
Answer:
(d) HCOOH

Question 94.
Which one of the following is formed as a product when Benzoic anhydride is hydrolysed?
(a) Benzoin
(b) Benzoic acid
(c) Benzyl alcohol
(d) Benzaldehyde
Answer:
(b) Benzoic acid

Question 95.
Consider the following statements.
(i) Carboxylic acids have higher boiling point than aldehyde and ketone due to the association of carboxylic acid.
(ii) Vinegar is 60 to 80% solution of acetic acid in water
(iii) Higher carboxylic acids are insoluble in water due to increased hydrophobic interaction of hydrocarbon part.
Which of the above statement is/are not correct’?
(a) (iii) only
(b) (ii) only
(c) (i) only
(d) (i) & (iii)
Answer:
(b) (ii) only

Question 96.
Which one of the following is formed when ethanoic acid is treated with HI and Red phosphorous?
(a) Ethane
(b) Ethene
(c) Ethyne
(d) Methane
Answer:
(a) Ethane

Question 97.
What will be the product formed when sodium acetate is treated with sodalime?
(a) C₂H₆
(b) CH₄
(c) CH₃COOH
(d) (CH₃CO)₂O
Answer:
(b) CH₄

Question 98.
The reaction of electrolysis of sodium acetate to form ethane is known as ………………..
(a) Kolbe’s electrolytic decarboxylation
(b) Perkin’s reaction
(c) Clemmenson reaction
(d) Cannizaro reaction
Answer:
(a) Kolbe’s electrolytic decarboxylation

Question 99.
Sodium formate solution on electrolysis gives at anode.
(a) Methane + CO₂
(b) Ethane + CO₂
(c) H₂ + CO₂
(d) Formic acid
Answer:
(c) H₂ + CO₂

Question 100.
Which one of the following is formed when acetic acid is heated with phosphorous pentoxide?
(a) CH₃COCH₃
(b) CH₃CONH₂
(c) CH₄
(d) (CH₃CO)₂O
Answer:
(d) (CH₃CO)₂O

Question 101.
The reaction of acetic acid with Cl₂ and red phosphorous is named as ………………
(a) Kolbe’s reaction
(b) Reimer – Tiemann reaction
(c) HeII – volhard – zelinsky reaction
(d) Knoevenagal reaction
Answer:
(c) HeII – volhard – zelinsky reaction

Question 102.
Which one of the following does not undergo friedel crafts reaction?

Answer:

Question 103.
Which one of the following can act as a reducing agent?
(a) C₆H₅COOH
(b) HCOOH
(c) CH₃COOH
(d) CH₃ – CH₂COOH
Answer:
(b) HCOOH

Question 104.
Consider the following statements.
(i) Carboxylic acids turn red litmus blue.
(ii) Carboxylic acids give brisk efferrescence with NaHCO3
(iii) Carboxylic acid is warmed with alcohol and conc. H₂SO₄ gives fruity odour ester.
Which of the above statement is/are not correct?
(a) (i) only
(b) (ii) only
(c) (iii) only
(d) (i) & (iii)
Answer:
(a) (i) only

Question 105.
Which is one the correct order of strength of carboxylic acid?


Answer:

Question 106.
The correct increasing order acid strength of carboxylic acid is …………
(a) F – CH₂ – COOH > I – CH₂ – COOH > CI – CH₂ – COOH > Br – CH₂ – COOH
(b) Br – CH₂ – COOH > F – CH₂COOH > I – CH₂COOH > Cl – CH₂ – COOH
(c) F – CH₂ – COOH > CI – CH₂COOH > Br – CH₂COOH > I – CH₂COOH
(d) Br – CH₂ – COOH > CI – CH₂ – COOH > I – CH₂COOH > F – CH₂COOH
Answer:
(c) F – CH₂ – COOH > CI – CH₂COOH > Br – CH₂COOH > I – CH₂COOH

Question 107.
The increasing order of acid strength is ………….
(a) CH₃COOH > CI₂CHCOOH > CCI₃CCOOH > ClCH₂COOH
(b) CI₃CCOOH > CI₂CH COOH > CICH₂COOH > CH₃COOH
(c) CH₂COOH < CI₂CH COOH < CCl₃CCOOH < ClCH₂COOH
(a) Cl₂CH – COOH < CCI₃COOH < ClCH₂COOH < CH₃COOH
Answer:
(b) CI₃CCOOH > CI₂CH COOH > CICH₂COOH > CH₃COOH

Question 108.
The relative acidities of various organic compounds are ……………
(a) RCOOH > ArOH > H₂O > ROH > RC ≡ CH
(b)RCCH > ArOH > ROH > H₂O > RCOOH
(c) ROH > R ≡ CH > ArOH > RCOOH > H₂O
(d) H₂O > ROH > RCOOH > ArOH > RC ≡ CH
Answer:
(a) RCOOH > ArOH > H₂O > ROH > RC ≡ CH

Question 109.
The correct order of the basicity of the leaving group is …………..

Answer:

Question 110.
The conversion of Ethyl acetate to propyl acetate by the action of propyl alcohol is named as
(a) Esterification
(b) Transesterfication
(c) Acid hydrolysis of ester
(d) Alkaline hydrolysis of ester
Answer:
(b) Transesterfication

Question 111.
Ethyl acetate undergoes self condensation in the presence of strong base to give ………………..
(a) Ethyl aceto acetate + Ethanol
(b) Ethyl aceto acetate + Acetic acid
(c) Ethyl aceto propionate + propanol
(d) Ethyl ethanoate + Ethanoic acid
Answer:
(a) Ethyl aceto acetate + Ethanol

Question 112.
Methyl cyanide on acid hydrolysis gives
(a) Acetyl chloride
(b) Acetic acid
(c) Acetamide
(d) Acetic anhydride
Answer:
(c) Acetamide

Question 113.
Which one of the following is the product formed when acetamide is treated with P₂O₅?
(a) Acetonitrile
(b) Methylamine
(c) Ethyl cyanide
(d) Methanamine
Answer:
(a) Acetonitrile

Question 114.
Identify the product formed when acetamide reacts with LiAIH₄?
(a) Methyl amine
(b) Aceto nitrite
(c) Ethyl amine
(d) Ethylcyanide
Answer:
(c) Ethyl amine

Question 115.
Which one of the following is used as a medicine in the treatment of gout?
(a) CH₃COOH
(b) C₆H₅COOH
(c) CH₃CONH₂
(d) HCOOH
Answer:
(d) HCOOH

Question 116.
Which one of the following is used as a coagulating agent for rubber latex?
(a) Ethanoyl chloride
(b) Butanoic acid
(c) Methanoic acid
(d) Benzoic acid
Answer:
(c) Methanoic acid

Question 117.
Which one of the following is used as food preservative?
(a) Sodium formate
(b) Sodium acetate
(c) Sodium benzoate
(d) Acetamide
Answer:
(c) Sodium benzoate

Question 118.
Which one of the following is used in detection and estimation of – OH and – NH₂ group in organic compounds?
(a) Acetic anhydride
(b) Acetyl chloride
(c) Acetamide
(d) Ethyl acetate
Answer:
(b) Acetyl chloride

Question 119.
Which one of the following is used in the preparation of medicine like aspirin and phenacetin?
(a) Acetyl chloride
(b) Acetic acid
(c) Acetamide
(d) Acetic anhydride
Answer:
(d) Acetic anhydride

Question 120.
Which one of the following is used in the preparation of Artificial fruit essences?
(a) Ethanoic acid
(b) Acetamide
(c) Ethyl acetate
(d) Acetic anhydride
Answer:
(c) Ethyl acetate

Question 121.
Acetone and acetaldehyde are differentiated by ………….
(a) NaOH + I²
(b) Ag(NH₃)₂⁺ (Tollens’s reagent)
(c) I²
(d) NaOH + NH₃
Answer:
(b) Ag(NH₃)₂⁺ (Tollens’s reagent)

Question 122.
The most suitable reagent for the conversion of is R – CH₂OH → RCHO …………..
(a) KMnO₄
(b) K₂Cr₂O₇
(c) CrO₃
(d) Pcc
Answer:
(d) Pcc

Question 123.
Which of the following will not give iodoform test?
(a) Isopropyl alcohol
(b) Ethanol
(c) Eth anal
(d) Benzyl alcohol
Answer:
(d) Benzyl alcohol

Question 124.
Products of the following reaction …….

(a) CH₃CHO + CH₃CH = CHO
(b) CH₃COOH + CH₃CH₂CHO
(c) CH₃COOH + HOOCCH₂CH₃
(d) CH₃COOH + CO₂
Answer:
(b) CH₃COOH + CH₃CH₂CHO

Question 125.
Identify the reagents X and Y are ………………

(a) X = MgCl₂ Y = CH₃CH = CH₂
(b) X = CH₃ MgCI Y = C₆H₅COCH₃
(c) X = CH₃ MgCI Y = (CH₃)₃C – OH
(d) X = C₆H₅ MgCI Y = (CH₃)₃C – OH
Answer:
(c) X = CH₃ MgCI Y = (CH₃)₃C – OH

Question 126.
Reduction of > C = O to – CH₂ can be carried out with ……………
(a) Ni
(b) Na/C₂H₅OH
(c) NH₂ – NH₂ + C₂HONa
(d) LiAIH₄
Answer:
(c) NH₂ – NH₂ + C₂HONa

Question 127.
Which of the following is incorrect?
(a) FeCl₃ is used in the detection of phenols
(b) Fehlings solution is used in the detection of aldehyde
(c) Tollen’s reagent is used in the detection of unsaturation
(d) NaHSO₃ is used in the detection of carbonyl compounds
Answer:
(c) Tollen’s reagent is used in the detection of unsaturation

Question 128.
Which of the following products is formed when Benzaldehyde is treated with CH₃MgBr and the addition product so obtained is subjected to acid hydrolysis?
(a) Secondary alcohol
(b) Primary alcohol
(c) Phenol
(d) Tertiary alcohol
Answer:
(a) Secondary alcohol

Question 129.
The reagent used to distinguish formaldehyde and acetaldehyde is …………..
(a) Tollen’s reagent
(b) Fehling’s solution
(c) Schiff’s reagent
(d) Caustic soda solution
Answer:
(d) Caustic soda solution

Question 130.
Which of the followìng will not give halo form test?
(a) Ethanal
(b) Ethanol
(c) Propan – 2 – one
(d) Pentan – 3 – one
Answer:
(d) Pentan – 3 – one

Question 131.
Which of the following does not turn schiff’s reagent to pink?
(a) Formaldehyde
(b) Benzaldehyde
(c) Acetone
(d) Acetaldehyde
Answer:
(c) Acetone

Question 132.
Which will not give acetamide on reaction with ammonia?
(a) Acetic acid
(b) Acetyl chloride
(c) Acetic anhydride
(d) methyl formate
Answer:
(d) methyl formate

Question 133.
The addition of HCN to carbonyl compounds is an example of ………….. reaction.
(a) N ucleophilic substitution
(b) Electrophil ic addition
(c) Nucleophilic addition
(d) Electrophilic substitution
Answer:
(c) Nucleophilic addition

Question 134.
Cinnamic acid is formed when C₆H₅CHO condenses with (CH₃CO)₂O in the presence of ……………
(a) Conc.H₂SO₄
(b) CH₃COONa
(c) Na metal
(d) Anhydrous ZnCI₂
Answer:
(b) CH₃COONa

Question 135.
The molecular formula of Urotropine is …………..
(a) (CH₂)₆N₄
(b) (CH₂)₄N₆
(c) (CH₂)₂N₂
(d) (CH₂)₆N₆
Answer:
(a) (CH₂)₆N₄

Question 136.
Bakelite is a thermosetting plastic produced by …………….
(a) HCHO + C₆H₅CH₂OH
(b) HCHO + C₆H₅OH
(c) CH₃CHO + C₆H₅OH
(d) HCHO + CH₃COCH₃
Answer:
(b) HCHO + C₆H₅OH

Question 137.
Aldehydes and ketones are reduced to hydrocarbon by the action of ………….
(a) LiAlH₄
(b) H₂ / Pd + BaSO₄
(c) Na + Hg/HCI
(d) NH₂ – NH₂ / C₂H₅ONa
Answer:
(d) NH₂ – NH₂ / C₂H₅ONa

Question 138.
What is the name of the reaction when benzaldehyde changes into Benzyl alcohol?
(a) Friedel – crafts reaction
(b) Kolbe’s reaction
(c) Cannizaro reaction
(d) Wurtz reaction
Answer:
(c) Cannizaro reaction

Question 139.
Aldehyde turns pink with …………..
(a) Benedict solution
(b) Schiff ‘s base
(c) Fehiing solution
(d) Tollen’s reagent
Answer:
(b) Schiff ‘s base

Question 140.
Which of the following would undergo aldol condensation?

Answer:

Question 141.
Which one of the following undergoes reaction with 50% NaOH solution to give the corresponding alcohol and acid?
(a) Butanal
(b) Phenyl methanal
(c) Phenol
(d) Ethanal
Answer:
(b) Phenyl methanal

Question 142.
Hexa methylene tetramine is used as ………………
(a) analgesic
(b) antipyretic
(c) Urinary antiseptic
(d) all of these
Answer:
(c) Urinary antiseptic

Question 143.
The compound which gives acetone on ozonolysis is …………
(a) CH₃ – CH = CH – CH₃
(b) (CH₃)₂C = C(CH₃)₂
(c) C₆H₅CH = CH₂
(d) CH₃ – CH = CH₂
Answer:
(b) (CH₃)₂C = C(CH₃)₂

Question 144.
Predict the product X in the sequence of the reaction


Answer:

Question 145.
From which of the following, tertiary butyl alcohol is obtained by the action of methyl magnesium iodide?
(a) HCHO
(b) CH₃COCH₃
(c) CH₃CHO
(d) CO₂
Answer:
(b) CH₃COCH₃

Question 146.
Tdentifý the product “C” in the sequence of the reaction.

(a) CH₃CH₂NH₂
(b) CH₃CH₂OH
(c) CH₂ = CH₂
(d) CH₃CHO
Answer:
(c) CH₂ = CH₂

Question 147.
O₃ reacts with CH₂ = CH₂ to form ozonide. On hydrolysis it forms …………….

Answer:

Question 148.
Ethyne on reaction with water in the presence of HgSO₄ and H₂SO₄ gives …………….
(a) Propanone
(b) Ethanal
(c) Ethane
(d) Ethanol
Answer:
(b) Ethanal

Question 149.
Which of the aldehyde is most reactive?
(a) C₆H₅CHO
(b) CH₃CHO
(c) HCHO
(d) CH₃ – CH₂ – CHO
Answer:
(c) HCHO

Question 150.
Acetaldehyde does not answer
(a) lodoform test
(b) Lucas test
(c) Benedict test
(d) Tollen’s reagent test
Answer:
(b) Lucas test

II. Fill In the blanks.

1. The aldehyde Pyridoxal function as a ………….
2. p – acetylated amino phenol is used to reduce ………….
3. The TUPAC name of CH₃ – CH = CH – CHO is ………….
4. The TUPAC name of CH₂ = CH – CHO is ………….
5. The formula of mesityl oxide is ………….
6. The name of is ………….
7. But – 2 – ene gives 2 moleafethanal by ………….
8. …………. Olefines give formaldehyde as one of the product.
9. Hydration of …………. in the presence of 40% dilute sulphuric acid and 1% HgSO₄ gives Ethanal.
10. Calcium formate on …………. gives methanal and CaCO₃.
11. Dry distillation of …………. gives propanone and CaCO₃.
12. Tn Rosenmund’s reduction reaction …………. is the catalyst and …………. is the catalytic poison.
13.  …………. selectively reduces alkyl cyanide to form imines which on hydrolysis gives aldehyde.
14. Side chain oxidation of toluene in the presence of KMnO₄ gives ………….
15. The oxidising agent used to convert toluene to benzaldehyde is ………….
16. Acetyl chloride reacts with …………. to form acetone.
17. Addition of …………. finds application in. the separation and purification of carbonyl compounds.
18. Aliphatic aldehyde except …………. react with an ethereal solution of ammonia to form aldimines.
19. Formaldehyde reacts with ammonia to form …………. which is used to treat urinary infection.
20. Nitration of Urotropine under controlled condition gives an explosive ………….
21. RDX is also called …………. or ………….
22. With ammonia, benzaldehyde form a complex condensation product called ………….
23. The oxidation of unsymmetrical ketone is governed by ………….
24. The reducing agent used in Clemmensen reduction is ………….
25. The reducing agent used in woif-kishner reduction is ………….
26. Symmetric diols are called ………….
27. Aldehydes which do not have …………. undergo disproportionation reaction (or) cannizaro reaction.
28. The reagent used in the conversion of Benzaldehyde to Benoin is ………….
29. In Knoevenagal reaction …………. act as the basic catalyst.
30. The formula of Benzal aniline (or) Schiffs base is ………….
31. Benzaldehyde condenses with N, N – dimethyl aniline in the presence of strong acids to form ………….
32. …………. is ammoniacal silver nitrate solution.
33.  …………. is a mixture of CuSO₄ + Sodium citrate + NaOH.
34. 40% aqueous solution of formaldehyde is known as …………..
35. Paraldehyde is used in medicine as ………….
36. Acetone is used in the manufacture of thermo softening plastic ………….
37. …………. is used in perfumery and as a hypnotic under the name hyphone.
38.  …………. cannot be prepared by grignard reagent since the acid contains only one carbon atom.
39. Most of carboxylic acid exist as …………. in its vapour state.
40. …………. is 6 to 8% solution of acetic acid in water.
41. …………. is used to convert acetic acid to ethane at 473 K.
42. …………. reaction is generally used for the preparation of esters of higher alcohol from that of a lower alcohol.
43. Formic acid is used in medicine for treatment of ………….
44. The conversion of acetamide to methylamine by the action of caustic alkali and Bromine is known as ………….
45. …………. is used as food preservative.
46. …………. is used in the detection and estimation of – OH, – NH₂, groups in organic compounds.
47. …………. is used in the preparation of artificial fruit essences.
48. The conversion of Benzene to Benzaldehyde by the action of carbon monoxide and HCl is known as ………….
49. The product formed when formaldehyde condensed with acetone is ………….
50. Benzaldehyde condenses with acetaldehyde to form ………….

Answer:

1. Coenzyme
2. Fever
3. But – 2 – enal
4. Prop – 2 – enal
5. (CH₃), C = CHCOCH₃
6. 3-Oxo pentanal
7. Ozonolysis
8. Terminal
9. Ethyne
10. Dry distillation
11. Calcium ethanoate
12. Pd, BaSO₄
13. Diisobutvl aluminum hydride
14. Benzoic acid
15. CrO₂Cl₂ Chromyl chloride
16.  Dimethyl cadmium
17.  NaHSO₃
18. Formaldehyde
19. Urotropinc (or) Hexamethylene tetramine
20. RDX (or) Research and development explosive
21. Cyclonite(or)cyclotrimethylene trinitramine
22. Hydrobenzamide
23. Popott’s rule
24. Zn + Hg / conc.HCl
25. NH₂ – NH₂ + C₂H₅ONa
26. Pinacol
27. a – hydrogen atom
28. Alcoholic KCN
29. Pyridine
30. C₆H₅CH = N – C₆H₅
31. Triphenyl methane dye or malachite green dye
32.  Tollen’s reagent
33. Benedict’s solution
34. Formalin
35. Hypnotic
36. Perspex
37. Acetophenone
38. Formic acid HCOOH
39. Dimer
40. Vinegar
41. HI + Red P
42. Transesterification
43. Gout
44. Hoff mann’s degradation
45. Sodium benzoate
46. Acetyl chloride
47. Ethyl acetate
48. Gattermann – koch reaction
49. 4 – hydroxy – butane – 2 – one
50. Cinnamaldehyde

III. Match the following.
Match the column I and II using the code given below the column.

Question 1.

Answer:
(a) 3 2 4 1

Question 2.

Answer:
(b) 3 1 4 2

Question 3.

Answer:
(c) 3 4 1 2

Question 4.

Answer:
(a) 2 3 4 1

Question 5.

Answer:
(d) 3 4 1 2

Question 6.

Answer:
(a) 2 3 1 4

Question 7.

Answer:
(a) 4 3 1 2

Question 8.

Answer:
(a) 3 4 1 2

Question 9.

Answer:
(a) 2 4 1 3

Question 10.

Answer:
(a) 3 1 4 2

Question 11.

Answer:
(a) 2 4 1 3

Question 12.

Answer:
(a) 2 3 4 1

IV. Assertion and reasons.

Question 1.
Assertion(A): In Rosenmund’s reduction, BaSO₄ act as catalyst pòison.
Reason (R): In Rosenmund’s reduction, BaSO₄ act as catalytic poison to pd catalyst so that aldehyde cannot be further reduced ti alcohol.
(a) Both A and R are correct and R is the correct explanation of A.
(b) Both A and R are correct but R is not correct explanation of A
(c) A is correct but R is wrong
(d) A is wrong but R is correct
Answer:
(a) Both A and R are correct and R is the correct explanation of A.

Question 2.
Assertion(A): Aldehydes and ketones have high high boiling point as compared to hydrocarbon and ether of comparable molecular mass.
Reason (R): It is due to weak molecular association in aldehydes and ketones arising out of the dipole – dipole interactions.
(a) Both A and R are correct and R is the correct explanation of A.
(b) Both A and R are wrong
(c) A is correct but R is wrong
(d) A is wrong but R is correct
Answer:
(a) Both A and R are correct and R is the correct explanation of A.

Question 3.
Assertion(A): The boiling point of aldehydes and ketones are much lower those of corresponding alcohols and carboxylic acids.
Reason (R): Alcohols and carboxylic acids possess intermolecular hydrogen bonding and so have high boiling point.
(a) Both A and R are correct but R is not the correct explanation of A.
(b) Both A and R are correct and R ¡s the correct explanation of A
(c) A is correct but R is wrong
(d) A is wrong but R is correct
Answer:
(b) Both A and R are correct and R ¡s the correct explanation of A

Question 4.
Assertion(A): Aldehydes and ketones have high dipole moment.
Reason (R): The carbonyl group of aldehydes and ketones contain a double bond between carbon and oxygen. Oxygen is more electronegative than carbon and it attracts the shared pair of electron which makes the carbonyl group as polar.
(a) Both A and R are correct and R is the correct explanation of A.
(b) Both A and R are correct but R is not the correct explanation of A
(c) A is correct but R is wrong
(d) A is wrong but R is correct
Answer:
(a) Both A and R are correct and R is the correct explanation of A.

Question 5.
Assertion(A): Addition of sodium bisuiphite finds application in the separation and purification of carbonyl compound.
Reason (R): The bisuiphite addition compound is water soluble and the solution is treated with mineral acid to regenerate the carbonyl compounds.
(a) Both A and R are correct and R is the correct explanation of A.
(b) Both A and R are correct but R is not the correct explanation of A
(c) Both A and R are wrong
(d) A is correct but R is wrong
Answer:
(a) Both A and R are correct and R is the correct explanation of A.

Question 6.
Assertion(A): Acetaldehyde does not undergo cannizaro reaction.
Reason (R): Cannizaro reaction is a characteristic of aldehyde having no α – H atom. Acetaldehyde contains 3 α – H atoms.
(a) Both A and R are correct and R is the correct explanation of A.
(b) Both A and R are correct but R. is not correct explanation of A
(c) A is correct but R is wrong
(d) A is wrong but R is correct
Answer:
(a) Both A and R are correct and R is the correct explanation of A.

Question 7.
Assertion(A): Acetaldehyde and acetone are readily undergo aldol condensation reaction in the presence of dilute base.
Reason (R): Aldehyde or ketone having α – hydrogen atom add together to give aldol or ketol.
(a) Both A and R are correct but R is not the correct explanation of A.
(b) Both A and R are correct and R is the correct explanation of A
(c) A is correct but R is wrong
(d) A is wrong but R is correct
Answer:
(b) Both A and R are correct and R is the correct explanation of A

Question 8.
Assertion(A): Carboxylic acids have higher boiling point than aldehyde and ketone of comparable molecular mass.
Reason (R): This is due to more association of carboxylic acid. Molecules through intermolecular hydrogen bonding.
(a) Both A and R are correct but R is not correct explanation of A.
(b) Both A and R are correct and R is the correct explanation of A
(c) A is correct but R is wrong
(d) A is wrong but R is correct
Answer:
(b) Both A and R are correct and R is the correct explanation of A

Question 9.
Assertion(A): Lower aliphatic carboxylic acids arc miscible with water but higher carboxylic acids are insoluble in water.
Reason (R): Lower carboxylic acids are able to form hydrogen bond with water whereas higher carboxylic acids have increased hydrophobic interaction of hydrocarbon part.
(a) Both A and R are correct and R is the correct explanation Of A.
(b) Both A and R are correct but R is not correct explanation of A
(c) A is correct but R is wrong
(d) A is wrong but R is correct
Answer:
(a) Both A and R are correct and R is the correct explanation Of A.

Question 10.
Assertion(A): Carboxylic acid do not give the characteristic reaction of carbonyl group as given by aldehyde and ketone.
Reason (R): The carbonyl carbon of carboxylic acid is involved in resonance.
(a) Both A and R are correct but R is not correct explanation of A.
(b) Both A and R are correct and R is the correct explanation of A
(c) Both A and R are correct and R is the correct explanation of A.
(d) Both A and R are correct but R is not correct explanation of A
Answer:
(c) Both A and R are correct and R is the correct explanation of A.

Question 11.
Assertion(A): Benzoic acid does not undergo friedel crafts reaction.
Reason (R): This is due to the strong deactivating nature of the carboxyl group
(a) Both A and R are correct and R is the correct explanation of A.
(b) Both A and R are correct but R is not the correct explanation of A
(c) A is correct but R is wrong
(d) A is wrong but R is correct
Answer:
(a) Both A and R are correct and R is the correct explanation of A.

Question 12.
Assertion(A): Formic acid can act as a strong reducing agent
Reason (R): Formic acid contains both aldehyde as well as an acid group.
(a) Both A and R are wrong
(b) A is correct but R is wrong
(c) A is wrong but R is correct
(d) Both A and R are correct and R is the correct explanation of A.
Answer:
(d) Both A and R are correct and R is the correct explanation of A.

Question 13.
Assertlon(A): Trichioro acetic acid is more acidic than acetic acid.
Reason (R): Cl^– is a electron withdrawing group and acidity increases with increasing number of electron withdrawing substituents on the α – carbon.
(a) Both A and R are correct and R is the correct reason of A.
(b) Both A and R are correct but R is not correct reason of A.
(c) A is correct but R is wrong
(d) A is wrong but R is correct.
Answer:
(a) Both A and R are correct and R is the correct reason of A.

V. Find the odd one out and give the reasons.

Question 1.
(a) Methanal
(b) Ethanal
(c) Phenyl metbanal
(d) Prop – 2 – enal
Answer:
(c) Phenyl metbanal
It is an aromatic aldehyde where as others are aliphatic aldehydes.

Question 2.
(a) Formic acid
(b) Acetic acid
(c) Benzoic acid
(d) Propanoic acid
Answer:
(d) Propanoic acid
It can act as reducing agent where as other acids are not act as reducing agents.

Question 3.
(a) HCHO
(b) C₆H₅CHO
(c) CCI₃CHO
(d) CH₃CHO
Answer:
(d) CH₃CHO
CH₃CHO. It contains α – H atom and undergoes aldol condensation where as others do not have α – H atoms and they undergo cannizaro reactions.

Samacheer Kalvi 12th Chemistry Carbonyl Compounds and Carboxylic Acids 2 Mark Questions and Answers

Question 1.
Write the name of the following compounds.
Answer:

Question 2.
What happens But – 2 – ene is ozonised followed by hydrolysis?
Answer:

Question 3.
Explain the action of ozone with 2 – methyl but – 2 – ene followed by hydrolysis with zinc?
Answer:

Question 4.
What happens when Ethyne is hydrolysed in the presence of HgSO₄ and H₂SO₄?
Answer:

Question 5.
How would you convert prop – 1 – yne to propanone?
Answer:
Prop – 1- lyne on hydrolysis with HgSO₄ and H₂SO₄ gives propanone as product.

Question 6.
Explain about the dry distillation of Calcium ethanoate.
Calcium ethanoate on dry distillation gives propanone as product.
Answer:

Question 7.
Explain Rosenmund reduction.
Answer:
Aldehydes can be prepared by the hydrogenation of acid chloride, in the presence of palladium supported by Barium sulphate. This reaction is called Rosenmund reduction.

In the above reaction, BaSO₄ act as a catalytic poison to palladium catalyst, so that aldehyde cannot be further reduced to alcohol.

Question 8.
Explain Stephen’s reaction.
Answer:
In Stephen’s reaction, alkyl cyanide are reduced using SnCl₂ / HCI, imines arc formed which on hydrolysis gives corresponding aldehyde.

Question 9.
Explain the action of Diisobutyl aluminium hydride (DIBAL – H) and H₂O with hex – 4 – en nitrile.
Answer:

Question 10.
Explain about Cattermann – koch reaction.
Answer:
Benzene reacts with carbon monoxide and HCl in the presence of AlCl₃ and CuCl to give Benzaldehyde. This reaction is known as Gattermann – Koch reaction.

Question 11.
How would you manufacture benzaldehyde from toluene?

This is the commercial method for the manufacture of Benzaldehyde.

Question 12.
Explain the action of dialkyl cadmium with acetyl chloride?
Answer:

Question 13.
Explain the nucleophilic addition of HCN with eth anal?
Answer:

Question 14.
Which reaction finds application in the separation and purification ofcarbonyl compound? Explain.

The bisuiphite compound is water soluble and the solution is treated with minerai acid to regenerate the carbonyl compound. So the above reaction is used in the separation and purification of carbonyl compound.

Question 15.
Complete the following reactions.
Answer:

Question 16.
What Is Clemmensen reduction ? Explain it.
Answer:
Aldehyde and ketones when heated with zinc amalgam and concentrated hydrochloric acid give hydrocarbons. This reaction is known as Clemmensen reduction.

Question 17.
Complete the following reactions.
Answer:

Question 18.
Explain Wolf Kishner reduction with suitable example.
Answer:
Wolf Kishner reduction:

Question 19.
How would you obtain chloroform from acetone?
Answer:
When acetone is treated with chlorine and alkali, chloroform is formed.

Question 20.
What happen when alcoholic KCN reacts with Benzaldehyde? (or) explain Benzoin condensation.
Answer:
Benzaldehyde reacts with alcoholic KCN to form Benzoin.

Question 21.
Explain about SchilT’s reagent test?
Answer:
Dilute solution of aldehyde when added to Schifl’s reagent (Rosaniline hydrochloride dissolved in water and its red colour decolourised by passing SO₂) yields its red colour. This is known as Schiffs’ test for aldehyde. Ketones do not give this test. Acetone however gives a positive test but slowly.

Question 22.
What are used of Urotropine? Give its structure.
Answer:
This is the structure of Urotropme (Hexamethylene tetramine)
1. Urotropine is used as a medicine to treat urinary infection.

2. Nitration ofUrotropine under controlled condition gives an explosive RDX (Research and development explosive). It is also called cyclonite or cyclotri methylene trinitramine.

Question 23.
Mention the uses of aromatic ketone.
Answer:

1. Acetophenone has been used in perfumery arid as a hypnotic under the name hyphone.
2. Benzophenone is used in perfumery and in the preparation of benzhydrol drop.

Question 24.
Write the structure and IUPAC name of the following compounds?

(i) Malonic acid

(ii) Succinic acid

(iii) Glutaric acid

(iv) Adipic acid

Answer:

Question 25.
Starting from methyl magnesium iodide, how would you prepare acetic acid?
Answer:

Question 26.
Convert phenyl magnesium bromide into Benzoic acid?
Answer:

Question 27.
Explain the hydrolysis reaction of the following with equation?

1. (CH₃CO)₂O
2. (C₆H₅CO)₂O

Answer:

Question 28.
Explain the action of alkaline potassium permanganate with toluene?
Answer:

Question 29.
Lower aliphatic carboxylic acids are miscible with water but higher carboxylic acids are insoluble in water. Give reason. (or) Acetic acid is soluble in water but hexanoic acid in insoluble in water. Why?
Answer:
Aliphatic acids are miscible with water due to the formation of hydrogen bonds with water. Higher carboxylic acids are insoluble in water due to increased hydrophobic interaction of hydrocarbon part. Thats why acetic acid is soluble in water whereas hexanoic acid is insoluble in water.

Question 30.
What is Vinegar? How will you get glacial acetic acid?
Answer:

1. Vinegar is 6 to 8% solution of acetic acid in water.
2. Pure acetic acid is called glacial acetic acid. Because it forms ice like crystal when cooled.

When aqueous acetic acid is cooled at 289.5 K, acetic acid solidifies and forms ice like crystals, where as water remains in liquid state and removed by filtration. This process is repeated to obtain glacial acetic acid.

Question 31.
Explain the action of the following reagents with acetic acid.

(i) PCI₅

(ii) SOCI₂

Answer:

Question 32.
Complete the following reactions.

Answer:

Question 33.
What happens when thionyl chloride reacts with benzoic acid?
Answer:
When Benzoic acid reacts with thionyl chloride, Benzoyl chloride is formed as product.

Question 34.
Explain Kolbe’s electrolytic decarboxylation.
Answer:
The aqueous solution of sodium or potassium salts of carboxylic acid on electrolysis gives alkanes at anode. This reaction is called kolbe’s electrolysis.

Question 35.
What happens when ammonia reacts with acetic acid?
Answer:

Question 36.
Explain the action of heat on acetic acid in the presence of phosphorous pentoxide.
Answer:

Question 37.
Explain the a – halogenation take place in acetic acid. (or) Explain IIell-Volhard-zelinsky reaction (HVZ reaction)?
Answer:

Carboxylic acids having an α – hydrogen are halogenated at the α – position on treatment with chlorine or bromine in the presence of small amount of red phosphorus to form a – halo carboxylic acids. This reaction is known as Hell – Volhard – Zelinsky reaction (HVZ reaction)

Question 38.
Acidity increases with increasing number of electron rithdrawing substituents on the α – carbon. Explain with example.
Answer:
Acidity increases with increasing number of electron withdrawing substituents on the α – carbon atom. For example,
Cl₃C – COOH > Cl₂CH – COOH > Cl – CH₂COOH > CH₃COOH
The effect of various, electron withdrawing groups on the acidity of a carboxylic acid follows the order,
– NO₂ > – CN > – F > – Cl > – Br > – I > Ph

Question 39.
Trichloro acetic acid is more acidic than acetic acid. Give reason.
Answer:
Cl^– is an electron withdrawing substituent. Acidity increases with the increasing number of electron withdrawing substituents on the α – carbon. So trichioro acetic acid is more acidic than acetic acid. CCI₃COOH is more acidic than CH₃COOH.

Question 40.
Fluoro acetic acid is more acidic than iodoacetic acid. Give reason.
Answer:
Acidity increases with increasing electro negativity of the substituents. F is more electro negative.
F – CH₂ – COOH > Cl – CH₂COOH > Br – CH₂ – COOH > 1 – CH₂ – COOH
So Fluoro acetic acid is more acidic than iodoacetic acid.

Question 41.
What are carboxylic acid derivatives? Give four examples.
Answer:
1. Carboxylic acid derivatives are compounds in which carboxylic acid – OH group is replaced by the atom or the group.

2.

Question 42.
Which is the best method to prepare acetyl chloride from acetic acid? why?
Answer:
Acetyl chloride is prepared from acetic acid by the action of thionyl chloride. This method is superior to others as the by products being gases escape leaving the acid chloride in the pure state.

Question 43.
Acetyl chloride fumes when exposed to air. Give reason.
Answer:
Acetyl chloride emit pale fumes of hydrogen chloride when exposed to air on account of their reaction with water vapour.

Question 44.
What happens when acetyl chloride is treated with ethanol?
Answer:

This reaction is also known as alcoholysis.

Question 45.
Explain ammonolysis reaction of acid chloride (or) what happens when ammonia reacts with acetvl chloride?
Answer:

Question 46.
What happens when acetic anhydride reacts with ethyl alcohol?
Answer:

Question 47.
Explain the reaction of ammonia with acetic anhydride.
Answer:

Question 48.
Complete the following reaction.
Answer:

Question 49.
What is transesterification? Explain with example.
Answer:
Esters of an alcohol can react with atiother alcohol in the presence of a mineral acid to give the ester of second alcohol. The interchange of alcohol portions of the esters is termed transesterification.

Question 50.
Explain the action of ammonia with ethyl acetate.
Answer:

Question 51.
How is ethyl acetate react with PCL₅?
Answer:

Question 52.
What happens when methyl cyanide is partially hydrolysed by cold conc. HCl?
Answer:

Question 53.
Explain the action of P₂O₅ with acetamide with equation.
Answer:

Question 54.
Describe Hoffmann degradation reaction. (or) How would you obtain methyl amine from acetamide?
Answer:
Acetamide reacts with bromine in the presence of caustic alkali to form a primary amine carrying one carbon less than the parent amide.

Question 55.
How would you preparate ethyl amine from acetamide?
Answer:

Question 56.
What are the used of acetyl chloride?
Answer:

1. Acetyl chloride is used as acetylating agent in organic analysis
2. it is used in the detection and estimation of – OH, – NH₂ groups in organic compounds.

Question 57.
Arrange the following compounds ¡n increasing order of their reactivity in nucleophilic addition reactions.

1. Ethanal, Propanal, Propanone, Butanone
2. Benzaldehyde, p – Tolualdehyde, p – Nitrobenzaldehyde, Acetophenone

Answer:

1. Butanone < Propanone < Propanal <Ethanal
2. Acetophenone < p – Tolualdehyde < Benzaldehyde < p – Nitrobenzaldehyde

Question 58.
Give the IUPAC names of the following compounds:

(i) PhCH₂CH₂COOH

(ii) (CH₃)₂C = CHCOOH

Answer:

1. 3 – Phenylpropanoic acid
2. 3 methylbut – 2 – enoje acid
3. 2 – methylcyclohexane carboxylic acid
4. 2, 4, 6 – Trinitorbenzoic acid or 2, 4, 6, – Trinitrobenzene carboxylic acid

Question 59.
Although phenoxide ion has more number of resonating structures than carboxylate ion, carboxylic acid is a stronger acid than phenol? Why?
Answer:
In carboxylate ion -ve charge is delocalised over two oxygen atoms whereas in phenoxide ion the -ve charge is delocalised over one oxygen atom. Therefore carboxylate ion is more stable than phenoxide ion and that is why carboxylic acids are more acidic than phenols.

Question 60.
How is aminoethane obtained from ethanal (acetaldehyde)?
Answer:

Question 61.
Why HCOOH does not give Hell – Voihard Zelinsky reaction but CH₃COOH does?
Answer:
CH₃COOH contains α – hydrogen atom and hence gives HVZ reaction but HCOOH does not contain an α – hydrogen atom and hence does not give HVZ reaction.

Question 62.
Write IUPAC names of the following.

Answer:

1. 3 – Methylpent – 2 – 3n 3 – 1, 5 – dioic acid
2. 6 – Bromo -3 – hydroxy- 5 – nitrobenzoic acid

Question 63.
Give chemical tests to distinguish between the following pair of compounds.

1. Phenol and Benzoic acid
2. Benzaldehyde and Acetophenone

Answer:

1. By adding feme chloride, phenol will give violet colour whereas benzoic acid will not react.
2. Adding I₂ and NaOH, Acetophenone will give yellow ppt. of iodoform whereas benzaldehyde will not react.

Question 64.
Give chemical tests to distinguish between the following pair of compounds.

1. Propanoyl chloride and propanoic acid
2. Benzaldehyde and Acetophenone

Answer:
1. On adding NaHCO₃, solution to each of them, propanoyl chloride will not react whereas propanoic acid will give brisk èfferevescence due to the evolution of CO₂.

2. On adding I₂ and NaOH, Acetophenone will give yellow ppt, of iodoform whereas benzaldehyde will not react

Question 65.
Give chemical tests to distinguish between the following pair of compounds.

1. Propanal and propanone
2. Benzaldehyde and Benzoic acid

Answer:

1. On adding Tollen’s reagent, propanal will give silver mirror whereas propanone does not react.
2. On adding NaHCO₃ solution, benzaldehyde will not react whereas benzoic acid will give brisk effervescence due to the evolution of CO₂.

Question 66.
Out of acetophenone and benzophenone, which one will give iodoform test? Write the reaction involved. (The compound should have CH₃CO group to show the iodoform test).
Answer:
Acetophenone (C₆H₅COCH₃) contains the group (CH₃CO) attached to the carbon atom and hence give lodoform test while benzophenone does not contain this group and hence does not give iodoform test.

Question 67.
Why does methanal not give aidol condensation while ethanol forms an aldol?
Answer:
This is because only those compounds which haie α – hydrogen atoms can undergo aldol condensation reactions. Ethanol possesses α – hydrogen and therefore undergoes aldol condensation. Methanal does not have α – hydrogen atoms, hence does not undergo aldol condensation reactions.

Samacheer Kalvi 12th Chemistry Carbonyl Compounds and Carboxylic Acids 3 Mark Questions and Answers.

Question 1.
Draw the structure and IUPAC name of the following compounds.

(i) Acrolein

(ii) Crotonaldehyde

(iii) Glyceraldehyde

Answer:

Question 2.
Draw the structure and IUPAC name of the following compounds.

(i)  Mesityl oxide

(ii) Acetophenone

(iii) Benzophenone

Answer:

Question 3.
Explain about the structure of carbonyl group.
Answer:
1. The carbonyl carbon

is sp² hybridised and carbon – oxygen bond is similar to carbon carbon double bond in alkenes. The carbonyl carbon forms three o bonds using their three sp² hybridised orbital. One of the sigma bond is formed with oxygen and the other two with hydrogen and carbon (in aldehydes) or with two carbons (in ketones). All the three ‘a’ bonded atoms arc lying on the same plane.

2. The fourth valence electron of carbon remains in its unhybridised ‘2p’ orbital which lies perpendicular to the plane and it overlaps with 2p orbital of oxygen to form a carbon – oxygen bond.

3. The oxygen atom has two non-bonding pairs of electrons, which occupy its remaining two P orbitais. Oxygen, the second most electro negative atom attracts the shaired pair of electron between the carbon and oxygen towards itself and hence the bond is polar. This polarisation contributes to the reactivity of aldehydes and ketones.

Question 4.
How are the following compounds are prepared by the dry distillation of calcium salt of carboxylic acids?

(i) Methanal

(ii) Ethanal

Answer:

Question 5.
How will you prepare benzaldehyde from methyl benzene? (or) Explain Etard reaction.
Answer:
When chromylchloridc is used as an oxidising agent, toluene gives benzaldehyde. This reaction is called Etard reaction. Acetic anhydride and CrO₃ can also be used for this reaction.

Question 6.
How would you prepare the following compounds by Friedel Crafts acylation?

(i) Acetophenone

(ii) Benzophenone

Answer:

Question 7.
Aldehydes and ketones have high boiling point as compared to hydrocarbons and ethers of comparable molecular mass and less than that of alcohols. Give reason.
Answer:
Aldehydes and ketones have high boiling point as compared to hydrocarbons and ethers of comparable molecular mass. It is due to the weak molecular association in aldehyde and ketone arising out of the dipole-dipole interactions.

These dipole – dipole interactions are weaker than intermolecular H – bonding. The boiling points of aldehydes and ketones are much lower than those of corresponding alcohols and carboxylic acids which possess inter molecular hydrogen bonding.

Question 8.
Explain the mechanism of nucleophilic addition reactions of aldehyde and ketone?
Answer:
1. Nucleophilic addition reaction is the most common reactions of aldehydes and ketones. The carbonyl carbon cames a small degree of positive charge.

2. Nucleophile such as CN^– can attack the carbonyl carbon and uses its bond pair to forni a new carbon – nucleophile’ a ‘bond, at the same time two electrons from the carbon – oxygen double bond move to the most electronegative oxygen atom.

3. This results in the formation of an alkoxide ion. In this process, the hybridisation of carbon changes from sp² to sp³

The tetrahedral intermediate can be protonated by water or an acid to form an alcohol.

Question 9.
How acetone reacts with the following reagents?

(i) NH₂OH

(ii) NH₂ – NH₂

(iii) C₆H₅NH – NH₂

Answer:

Question 10.
What is Urotropine? How is It prepared? Mention Its structure and uses.
Answer:
1. Urotropine is hexamethylene tetramine. N

2. Formaldehyde reacts with ammonia to form hexamethylene tetramine, which is called Urotropine. HC CH1 CH

3. Urotropine is used as a medicine to treat urinary infection.

4. Nitration of Urotropine under controlled condition gives an explosive RDX (Research and development explosive). It is also called cyclonite or cyclotri methylene trinitramine.

Question 11.
What is popoff ‘s rule? Explain with an example.
Answer:
The oxidation of unsymmetrical ketones is governed by Popoff’s rule. It states that during the oxidation of an unsymmetrical ketone, a (C – CO) bond is cleaved in such a way that the keto group stays with the smaller alkyl group. Example:

Question 12.
Explain the action of magnesium amalgam and water with acetone?
Answer:

Question 13.
Describe crossed aldol condensation with two examples.
Answer:
Aldol condensation can takes place between two different aldehyde or ketones or between one aldehyde and one ketone is called crossed or mixed aldol condensation. E.g.,

Question 14.
Explain Claisen – Schmidt condensation.
Answer:
Benzaldehye condenses with acetaldehyde or acetone in the presence of dil. alkali at room temperature to form unsaturated aldehyde (or) ketone. This type of reaction is called Claisen – Schmidt condensation.

Question 15.
What is crossed cannizaro reaction? Explain It.
Answer:
When Cannizaro reaction (Auto redox reaction) takes place between two different aldehyde, the reaction is called as crossed cannizaro reaction.

In crossed cannizaro reaction more reactive aldehyde is oxidized and less reactive aldehyde is reduced.

Question 16.
How will you prepare malachite green dye from Benzaldehyde?
Answer:
Benzaldehyde condenses with tertiary aromatic amines like N, N – dimethyl aniline in the presence of strong acids to triphenyl methane dye.

Question 17.
How Is chlorine react with Benzaldehyde?

 

• In the presence of catalyst
• In the absence of catalyst

Answer:

Question 18.
Explain about 3 test for aldehyde
Answer:
1. Tollen’s reagent test:
When an aldehyde is warmed with Tollens reagent(Ammonical silver nitrate), a bright silver mirror is produced due to the formation of silver metal. This reaction is also called silver mirror test for aldehydes.

2. Fehlings solution Test:
Fehlings solution is prepared by mixing equal volumes of Fehlings solution ‘A’ containing aqueous copper sulphate and Fehlings solution ‘B’ containing alkaline solution of sodium potassium tartarate (RocheLle salt) When aldehyde is warmed with Fehlings solution deep blue colour solution is changed to red precipitate of cuprous oxide.

3. Benedict’s solution Test:
Benedict’s solution is a mixture of CuSO₄ + sodium citrate + NaOH. Cu²⁺ is reduced by aldehyde to give red precipitate of cuprous oxide.

Question 19.
Mention the uses of formaldehyde.
Answer:

1.   40% aqueous solution of formaldehyde is called formalin. It is used for preserving biological specimens.
2. Formalin has hardening effect, hence it is used for tanning.
3. Formalin is used in the production of thermo setting plastic known as bakelite, which is obtained by heating phenol with formalin.

Question 20.
What are the uses of acetaldehyde?
Answer:

1. Acetaldehyde is used for silvering of mirrors
2. Paraldehyde is used in medicine as a hypnotic.
3. Acetaldehyde is used in the commercial preparation of organic compounds like acetic acid, ethyl acetate etc.,

Question 21.
Write about the uses of Acetone.
Answer:

1. Acetone is used as a solvent, in the manufacture of smokeless powder (cordite)
2. It is used as a nail polish remover.
3. It is used in the preparation of suiphonal, a hypnotic.
4. It is used in the manufacture of thermosoftening plastic Perspex.

Question 22.
What are the uses of Benzaldehyde?
Answer:

1. as a flavoring agent
2. in perfumes
3. in dye intermediates
4. as starting material for the synthesis of several other organic compounds like cinnamaldehyde, cinnamic acid, benzoyl chloride etc.

Question 23.
Carboxylic acids have higher boiling pint than aldehyde, keton and even alcohols of comparable molecular masses. Give reason.
Answer:
Carboxylic acids have higher boiling point due to more association of acid molecules through inter molecular hydrogen bonding.

In fact, most of the carboxylic acids exist as dimer in its vapour phase.

Question 24.
What happens when ethanoic acid reacts with the following reagents?

1. LiAIH₄
2. Red P, Hl

Answer:
1. When ethanoic acid reacts by LiAIH₄, partial reduction take place and ethanol is formed as a product.

2. When ethanoic acid is treated with HI and red phosphorous, complete reduction take place and alkane is formed as a product.

Question 25.
Explain the action of sodalime with sodium acetate. Name the type of reaction involved in ¡t.
Answer:
When sodium acetate is treated with sodalime, methane is formed.

Removal of CO₂ from carboxyl group take place in it and this is called decarboxylation

Question 26.
Explain about electrophilic substitution in Benzoic acid with example.
Answer:
Benzoic acid undergoes electrophilic substitution. The carboxyl group is a deactivating and meta directing group.
1. Halogenation.

2. Nitration

3. Sulphonation

Quesiton 27.
Formic acid act as reducing agent. Prove this statement.
Answer:
1. Formic acid contains both an aldehyde as well as an acid group. Hence, like other aldehydes, formic acid can easily be oxidised and therefore acts as a strong reducing agent.

2. Formic acid reduces Tollen’s reagent (ammonical silver nitrate solution) to metallic silver.

3. Formic acid reduces Fehling’s solution. It reduces blue coloured cupric ions to red coloured cuprous ions.

Question 28.
Give three test for carboxylic acid.
Answer:

1. In aqueous solution, carboxylic acid turn blue litmus red.
2. Carboxylic acids give brisk effervescence with. sodium bicarbonate due to the evolution of carbon – di – oxide.
3. When carboxylic acid is warmed with alcohol and conc H₂SO₄ it forms an ester, which is detected by its fruity odour.

Question 29.
Write a note about acidity of carboxylic acids.
Answer:
1. Carboxylic acids undergo ionisation to produce W and carboxylate ions in aqueous solution. The carboxylate ion is stabilised by resonance which make the Carboxylic acid to donate the proton easily.

2. The resonance structure of carboxylate ion are given below.

3. The strength of carboxylic acid can be expressed in terms of the dissociation constant(K_a):

The stronger the acid, the large will be its K_a value.
PK_a = – log K_a
A strong acid will have higher k_a value but smaller pK^a value, the reverse is true for weak acid.

Question 30.
Formic acid is more stronger than acetic acid. Justify this statement. The electron releasing groups (+I groups) increase the relative charge on the carboxylate ion and destabilise it and hence the loss of proton becomes difficult.
+ I groups are CH₃, – C₂H₅, – C₃H₇

Question 31.
Explain the order of relative reactivity of acid derivatives.
Answer:
1. The reactivity of the acid derivatives follows the order

2. The above order of reactivity can be explained in terms of
Basicity of the leaving group
(b) Resonance effect

3. Weaker bases are good leaving groups. Hence acyl derivatives with weaker bases as leaving groups (L) can easily rupture the bond and are more reactive. The correct order of the basicity of the leaving group is

Hence the reverse is the order of reactivity.

4. Lesser the electronegativity of the group, greater would be the resonance stabilization as shown below.

This effect makes the molecule more stable and reduces the reactivity of the acyl compound. The order of electronegativity of the leaving groups follows the order – Cl > – OCOR > – OR > – NH₂. Hence the order of reactivity of the acid derivatives with nucleophilic reagent follows the order
Acid halide > Acid anhydride> esters> Acid amides

Question 32.
Explain the following reaction with acetyl chloride

1. ammonolysis.

Answer:
Reaction with ammonia is known as arninonolysis

Question 33.
Explain the action of the following reagents with acetyl chloride?

1. Pd / BaSO₄
2. LiAIH₄

Answer:

Question 34.
Describe about Claisen condensation.
Answer:
Esters containing at least one α – hydrogen atom undergo self condensation in the presence of a strong base such as sodium ethoxide to form β – keto ester. This reaction is known as Claisen condensation.

Question 35.
Acid amides are generally amphoteric in nature. Justify this statement.
Answer:
1. Amides behave both as weak acid as well as weak base and thus show amphoteric character. This can be proved by the following reactions.

2. Acetamide (as base) reacts with hydrochloric acid to form salt

3. Acetamide (as acid) reacts with sodium to form sodium salt and hydrogen gas is liberated

Question 36.
Mention the uses of formic acid?
Answer:
Formic acid. It is used

1. for the dehydration of hides.
2. as a coagulating agent for rubber latex
3. in medicine for treatment of gout
4. as an antiseptic in the preservation of fruit juice

Question 37.
What are the uses of acetic acid?
Answer:
Acetic acid is used

1. as table vinegar
2. for coagulating rubber latex
3. for manufacture of cellulose acetate and poiy vinylacetate

Question 38.
Indicate the uses of Benzoic acid.
Answer:
Benzoic acid is used

1. as food preservative either in the pure form or in the form of sodium benzoate
2. in medicine as an urinary antiseptic
3. for manufacture of dyes

Question 39.
What are the uses of acetic anhydride?
Answer:
Acetic anhydride is used

1. acetylating agent
2. in the preparation of medicine like aspnn and phenacetin
3. for the manufacture plastics like cellulose acetate and poly vinyl acetate.

Question 40.
Mention the uses of Ethyl acetate?
Answer:
Ethyl acetate is used

1. in the preparation of artificial fruit essences.
2. as a solvent for lacquers.
3. in the preparation of organic synthetic reagent like ethyl acetoacetate.

Question 41.
Give reasons for the following.

1. Carboxylic acids do not give characteristic reactions of carboxyl group
2. Treatment of benzaldehyde with HCN gives a mixture of two isomers which cannot be separated even by careful fractional distillation.
3. Sodium bisuiphite is used for the purification of aldehydes and ketones.

Answer:
1. It is due to reasonance

2. It is because we get two optical isomers which have same physical properties, therefore, cannot be separated by fractional distillation.

3. Aldehydes and ketones form addition compounds with NaHSO₃ whereas any impurities do not. On hydrolysis, we get pure aldehydes and ketones back again.

Question 42.

(i) Describe the preparation of acetic acid from acetylene.

(ii) How can the following be obtained from acetic acid:

(a) Acetone

(b) Acetaldehyde

(iii) In what way can acetic acid be distinguished from acetone?

(iv) Why carboxylic acid do not give the characteristic reactions of a carbonyl group?

Answer:

(iii). Add I₂ and NaOH. Acetone will give yellow precipitate of iodoform whereas acetic acid does not react to give any yellow precipitate.(or) Add sodium bicarbonate solution Acetone will not react, but acetic acid will give brisk effervescence due to the evolution of CO₂.

(iv). Carboxylic acid does not give the characteristic reactions of carbonyl group due to reasonance effect by the virtue of which it does not have free

carbonyl group.

Question 43.
Account for the following

1. Cl – CH₂COOH is a stronger acid than CH₃COOH
2. Carboxylic acids do not give reactions of carbonyl group.

Answer:
1. MonochLoroacetic acid is comparatively stronger acid than acetic acid. This is due to – Cl as a – I group

2. Carboxylic acids do not give reactions of carbonyl group because the lone pair of electrons on the oxygen attached to hydrogen in the – COOH group are involved in resonance, which makes the carbon less electrophilic.

Question 44.
A group of students were given to study the properties of aldehydes and ketones in the lab. They recorded a few observation of their physical properties.

1. Why are aldehydes more reactive and moreioiuble than ketones?
2. What values of students are seen from the above act?

Answer:

1. Aldehydes are more soluble in water because they form hydrogen bond with water molecule.
2. Critical thinking

Question 45.
How will you distinguish between methanol and ethanol?
Answer:
By Iodoform test:
Ethanol having α – methyl group will give yellow ppt of iodoform whereas methanol, which do not have α – methyl group, will not give ppt. of iodoform.

Question 46.
There are two – NH₂ group in semicarbazide. However, only one is involved in the formation of semicarbazone. Why?
Answer:
Although semicarbazide has two – NH₂ groups but only one of them is involved in resonance as shown below.

As a result, e density on one of the – NH₂ group is reduced and hence it does not act as nucleophile. One pair of the other – NH₂ group is not involved in resonance and hence it is available for nucleophilic attack.

Question 47.
Explain why o – hydroxybenzaldehyde is a liquid at room temperature while p – hydroxybenzaldehyde is a high melting solid?
Answer:
Due to intramolecular H – bonding orthohydroxy benzaldehyde exists as discrete molecule whereas due to intermolecular H – bonding, p – hydroxybenzaldehyde exists as associated molecules. To break these intermolecular H – bonds, a large amount of energy is needed.

Consequently, p – hydroxybenzaldehyde has a much higher m.pt. and b.pt. than that of o – hydroxy benzaldehyde. As a result, o -hydroxy benzaldehyde is a liquid at room temperature while p – hydroxy benzaldehyde is a high melting solid.

Question 48.
A compound ‘X’ (C₂H₄O) on oxidation gives ‘Y’ (C₂H₄O₂), ‘X’ undergoes haloform reaction. On treatment with HCN ‘X’ form a product ‘Z’ which on hydrolysis gives 2 – hydroxy propanoic acid.

1. Write down the structures of ‘X’ and ‘Y’
2. Name the product when ‘X’ reacts with dii NaOH.
3. Write down the equations for the reaction involved.

Answer:

Structure of Y (CH₃COOH)

Question 49.

1. How will you prepare

• Acetic anhydride and
• Acetyl chloride from acetic acid?

Write the reactions involved in each case.
2. Why is the boiling point of an acid anhydride higher than the acid from which it is derived?
Answer:
1.

2. Acid anhydrides are bigger sized molecules than the corresponding acids, therefore have more surface area, more van der Waals’ forces of attraction and hence higher boiling points.

Question 50.
Suggest a reason for the large difference in the boiling point of butanol and butanal, although they have the same solubility in water.
Answer:
The b.pt. of butanol is higher than that of butanal because butanol has strong intermolecular H – bonding while butanal has weak dipole – dipole interactions. However both of them will form H – bond with water and hence are soluble.

Samacheer Kalvi 12th Chemistry Carbonyl Compounds and Carboxylic Acids 5 Mark Questions and Answers

Answer the following questions.

Question 1.
Explain the action of ammonia with the following compounds.

Answer:
(i).  Formaldehyde reacts with ammonia to form hexa methylene tetramine, which is also known as UrotroDine.

Question 2.
Explain the mechanism of aldol condensation.
Answer:
In presence of dilute base NaOH, or KOH, two molecules of an aldehyde or ketone having α – hydrogen add together to give 3 – hydroxyl aldehyde (aldol) or – hydroxyl ketone (ketol). The reaction is called aldol condensation reaction.

Mechanism
The mechanism of aldol condensation of acetaldehyde takes place in three steps.
Step 1:
The carbanion is formed as the α – hydrogen atom is removed as a proton by the base.

Step 2:
The carbanion attacks the carbonyl carbon of another unionized aldehyde to form an alkoxide ion.

Step 3:
The alkoxide ion formed is protonated by water to form aldol.

The aldol rapidly undergoes dehydration on heating with acid to form a, f3 unsaturated aldehyde.

Question 3.
Explain the mechanism of Cannizaro reaction.
Answer:
1. In the presence of concentrated aqueous or alcoholic alkali, aldehydes which do not have α – hydrogen atom undergo self oxidation and reduction to give a mixture of alcohol and a salt of carboxylic acid. This reaction is called Cannizaro reaction.

2. Benzaldehyde on treatment with concentrated NaOH (50%) gives benzyl alcohol and sodium benzoate.

Mechanism
Cannizaro reaction involves three steps.
3. Step 1:
Attack of OH^– on the carbonyl carbons.

4. Step 2:
Hydride ion transfer

5. Step 3:
Acid – base reaction

Question 4.
Explain

1. Perkin’s reaction
2. Knocvenagal reaction.

Answer:
1. Perkin’s reaction
When an aromatic aldehyde is heated with an aliphatic acid anhydride in the presence of the sodium salt of the acid corresponding to the anhydride, condensation takes place and an α, β unsaturated acid is obtained. This reaction is known as Perkin’s reaction.

2. Knoevenagal reaction

Question 5.
Explain about electrophilic substitution reactions of Benzaldehyde and acetophenone.
Answer:

Question 6.
How would you prepare acetic acid from the following compounds.

1. Ethyl alcohol
2. Methyl cyanide
3. Ethyl acetate

Answer:

Question 7.
What is esterification? Explain the mechanism of esterification.
Answer:
When carboxylic acids are heated with alcohols in the presence of conc. HCI (or) dry HCI gas, esters are formed. This reaction is reversible and is called esterification.

Question 8.
An organic compound (A) (molecular formula C₈H₁₆O₂) was hydrolysed with dilute sulphuric acid to give a carboxylic acid (B) and an alcohol (C). Oxidation of (C) with chromic acid produced (B). (C) on dehydration gives but -1-ene. Write equations for the reactions involved.
Answer:
The relevant equations for all the reactions involved may be explained as follows.

Question 9.
An organic compound (A) of molecular formula CH₆ reacts with Br₂ in the presence of FeCI₃ gives (B) of formula C₆HBr. B on treatment with mg in the presence of dry ether gives (C) compound (C) on treatment with dry ice followed by hydrolysis gives a compound (D) of molecular formula C₇H₆O₂. Identify A,B,C,D and explain the reactions involved.
Answer:

Question 10.
A simplest aromatic hydrocarbon (A) reacts with methyl chloride in the presence of AICI₃ gives (B) C₇H₈. Compound (B) reacts with Br₂ along with light gives (C) of molecular formula C₇H₇Br (C) reacts with alcohol KCN gives (D) (C₈H₇N) (D) on acid hydrolysis gives (E) of formula C₈H₈O₂. Identify A,B,C,D,E and explain the reactions involved.
Answer:

Question 11.
An organic compound (A) is a calcium salt of acetic acid. (A) on dry distillation gives (B) of formula C₃H₆O. (B) on reaction with LiAIH₄ gives (C) of formula C₃H₈O (C) on heating with conc. H₂SO₄ gives (D) of molecular formula C₃H₆. Identify A,B,C,D and explain the reaction involved.
Answer:

Question 12.
An organic compound (A) of molecular formula C₇H₈O on oxidation with alkaline KMnO₄ gives (B) of formula C₇H₆O. (B) on reaction with CI₂ in the presence of catalyst FeCl₃ gives (C) of formula C₇HOCl. (B) on reaction with CI₂ in the absence of catalyst gives C₇H₅OCI. Identify A,B, C,D and explain the reaction involved.
Answer:

Question 13.
An organic compound (A) of molecular formula C₇H₆O reacts with acedaldehyde In the presence of sodium ethoxide gives (B) of formula C₉H₈O an unsaturated aldehyde. Compound (A) reacts with acetic anhydride in the presence of sodium acetate gives (C) and (D) of formula C₉HO₂ & C₂H₄O₂ respectively. Identify AB,C,D and explain the reaction involved.
Answer:
1. From the molecular formula (A) is identified as Benzaldehyde C₆H₅CHO.Benzaldehyde reacts with acetaldehyde to give cinnamaldehyde as B in Claisen condensation reaction.

2. Benzaldehyde reacts with acetic anhydride (Oerkin’s reaction) to give cinnamic acid (C) as product.

Question 14.
An aromatic aldehyde (A) of molecular C₇H₆O reacts with acidified KMnO₄ to give (B) of molecular formula C₇H₆O₂ calcium salt of compound (B) on dry distillation gives (C) of molecular formula C₁₃H₁₀O Compound (C) on Clemmenson’s reduction, gives (D) of formula C₁₃H₁₂O. Identify A,B,C,D and explain the reaction involved.
Answer:
1. From the molecular formula (A) is identified as Benzaldehyde C₆H₅CHO.Benzaldehyde on reaction with acidified KMnO₄ undergoes oxidation to give Bcnzoic acid as compound (B)

2. Calcium salt of Benzoic acid on dry distillaiton gives Benzophenone as compound (C)

3. Benzophenone undergoes Clemmenson reduction in the presence Zn amalgam and HCI gives Diphenyl methane as (D)

Question 15.
A simplest aromatic hydrocarbon (A) of formula C₆H₆ reacts with Bromine to gives (B) of molecular formula C₆H₅Br. (B) on treatment with magnesium metal in the presence of dry ether gives (C) . (C) on reaction with formaldehyde followed by acid hydrolysis gives (D) of formula C₇H₈O. Identify AB,C,D and explain the reaction involved.
Answer:
1. From the molecular formula (A) is identified as Benzene C6H6, Benzene reacts with Bromine to give bromobenzene as (B)

2. Bromobenzene reacts with Mg in the presence of dry ether gives phenyÍ magnesium bromide (Grignard reagent) as compound (C)

3. Phenyl magnesium bromide react with formaldehyde followed by acid hydrolysis gives Benzyl alcohol as product (D)

Question 16.
An organic compound (A) of molecular formula C₂H₃N on acid hydrolysis gives (B) of molecular formula C₂H₄O₂ calcium salt of (B) gives (C) of molecular formula C₃H₆O. Compound (C) on reduction of hydrazine and sodium ethoxide gives (D) of molecular formula C₃H₈. Identify A,B,C,D and explain the reaction involved.
Answer:
1.
2.
3. Wolf – Kishner reduction

Question 17.
An organic compound (A) of molecular formula C₇H₈ on reaction with hot alkaline KMnO₄ gives (B) of formula C₇H₆O₂ which gives brisk effervescence with NaHCO₃ solution. (B) on reaction with sodium hydroxide gives (C) of formula C₇H₅O₂Na. Compound (C) on treatment with sodalime gives (D) the simplest aromatic hydrocarbon.
Answer:
1. From the molecular formula (A) is identified as Toluene. Toluene on treatment with hot alkaline KMnO₄, oxidation take place and the product (B) formed is Benzoic acid.

2. Benzoic acid reacts with sodium hydroxide to give sodium benzoate as compound (C)

3. Sodium benzoate on reaction with sodalime (NaOH + CaO) decarboxylation take place and the product (D) formed is Benzene.

Question 18.
An organic compound (A) molecular formula C₃H₆O is resistant to oxidation but form a compound (B) (C₃H₈O) on reduction (B) reacts with HBr to form a bromide (C) which on treatment with alcoholic KOH forms an alkene (D) (C₃H₆). Deduce the structures of A,B,C and D.
Answer:

Question 19.
An organic compound (A) of molecular formula C₆H₆O gives violet colour with neutral FeCI₃. (A) on reaction with zinc dust gives (B) of formula C₆H₆ (B) on treatment with acetvl chloride in the presence of anhydrous AICI₃ gives (C) of formula C₈HO. (C) on Clemmenson reduction gives (D) of formula C₈H₁₀O. Identify A,B,C,D and explain the reaction involved.
Answer:

Question 20.
An organic compound (A) of molecular formula C₃H₆O reduces Tollen’s reagent on reaction with methyl magnesium bromide followed by acid hydrolysis gives (B) of formula C₄H₁₀O. (B) gives blue colour in victor meyer test. (B) on reaction with Cu at 573 K gives (C) of formula C₄H₈O (C) on reaction with hydrazine and sodium ethoxide gives (D) of molecular formula C₄H₁₀. identify A,B,C,D and explain the reactions involved.
Answer:
1. An organic compound (A) reduces Tollen’s reagent it must be an aldehyde. From the formula, it is identified as CH₃ – CH₂ – CHO propanal.

2. Propanal on reaction with methyl magnesium bromide followed by acid hydrolysis gives (B) as Butan – 2 – ol. It must be a secondary alcohol and gives blue colour with victor meyer’s test. H

3.

4. Wolf – Kishner reduction.

Question 21.
An organic compound (A) of molecular formula C₇H₆O₂ reacts with PCI₅ to give (B) of formula C₇H₅OCl (B) on treatment with ammonia gives (C) of formula C₇H₇NO (C) on treatment with phosphorous pentoxide gives (D) of formula C₇H₅N. Identify A,BC,D and explain the reactions involved.
Answer:

Question 22.
An organic compound (A) of molecular formula C₃H₆ on hydration in the presence of H₂SO₄ gives (B) C₃H₅O which gives blue colour In victor meyer’s test. (B) on treatment with Cu at 573 K gives C₃H₆O a compound (C) on self condensation in the presence of magnesium amalgam and water gives (D) of formula C₆H₁₄O₂. Identify A,B,C,D and explain the reaction involved.
Answer:

Question 23.
An organic compound (A) of molecular formula C₂H₄O reduces tollen’s reagent to silver mirror. (A) on treatment with C₂H₅MgBr followed by acid hydrolysis gives (B) of formula C₄H₁₀O. (B) on reaction with Cu at 573 K gives (C) of formula C₄H₈O which does not reduce tollen’s reagent but answers iodoform test. Identify A,B,C,D and explain the reaction involved.
Answer:

Question 24.
An unknown aldehyde ‘A’ on reacting with alkali gives a b – hydroxy – aldehyde, which loses water to form an unsaturated aldehyde, 2 – butenal. Another aldehyde ‘B’ undergoes disporportionation reaction in the presence of conc. alkali to form products C and D. C is – an aryl alcohol with formula C₇H₈O.

1. Identify A and B.
2. Write the sequence of reactions involved
3. Name the product, when ‘B’ reacts with Zn amalgam and hydrochloric acid.

Answer:

1. ‘A’ is acetaldehyde ‘B’ is Benzaldehyde

2. reactuib are shown above.

Question 25.
An organic compound (A) of molecular formula C₄H₈ is symmetric alkene. (A) on ozonolysis gives 2 moles (B) of molecular formula C₂H₄O. (B) on reaction with ammonia gives (C) of molecular formula C₂H₅N.
Answer:
1. (A) is a symmetric alkene. From the molecular formula, it is identified as But – 2 – ene

2. But – 2 – ene on ozonolysis gives 2 moles of acetaldehyde as product (B)

3.

Question 26.
An organic compound (A) of molecular formula C₂H₄O₂ gives brisk effervescence with sodium carbonate. (A) on reaction with thiony chloride gives (B) of formula C₂H₃OCI. (B) on reaction with Pd/BaSO₄ gives (C) of molecular formula C₂H₄O that reduces Tollen’s reagent to silver mirror. (C) on reaction with dilute NaOH gives (D) of molecular formula C₄H₈O₂. identify A,B,C,D and explain the reactions involved.
Answer:
1. (A) gives brisk effervescence with Na₂CO₃ means it must be a carboxylic acid. So (A) must be CH₃COOH Acetic acid.

2. Acetic acid reacts with thionyl chloride to give acetyl chloride CH₃COCI as (B)

3. Acetyl chloride reacts with Pd/BaSO₄, it undergoes Rosenmund’s reduction to give acetaldehyde as (C)

4. When acetaldehyde is warmed with dilute NaOH, it undergoes aldol condensation to

Question 27.
An organic compound (A) of molecular formula C₇H₈ reacts with CI₂ in the presence of ho light gives (B) of formula C₇H₆C₁₂. (B) on hydrolysis at 373 k gives (C) of formula C₇H₆O. (C) on treatment with 50% NaOH gives (D) and (E). Identify A,B,CD,E and explain the reactions involved.
Answer:
1. From the molecular formula (A) is identified as Toluene. ToÍuene reacts with Cl₂ in the presence of light gives Benzal chloride as (B)

2. Benzal chloride on hydrolysis at 373 k gives Benzaldehyde as (C)

3. Benzaldehyde when warmed with dilute NaOH undergoes cannizaro reaction to give Benzyl alcohol (D) and sodium benzoate (E)

Question 28.
An organic compound (A) of molecular formula C₂H₃OCI on reaction with pd and BaSO₄ gives (B) of formula C₂H₄O. (B) on reaction with LiAIH₄ gives (C) of formula C₂H₆O. (B) on reaction with 12 and NaOH gives (D) of formula CH₂ONa and iodoform. identify A,B,CD and explain the reactions involved.
Answer:
1. From the molecular formula (A) is identified as CH₃COCl (Acetyl chloride)

2. Acetyl chloride on treatment with Pd and BaSO₄ gives acetaldehyde CH₃CHO as (B)

3. Acetaldehyde on reaction with LiAIH₄ gives ethyl alcohol as (C)

4. Acetaldehyde when treated with I₂ and NaOH gives sodium formate (D) and iodoform CHI₃ as products.

Question 29.
An organic compound (A) of molecular formula C₇H₆O gives brisk effervescence with Na₂CO₃. Sodium salt of (A) on treatment with sodalime gives (B) a simplest aromatic hydrocarbon. (B) on reaction with acetyichioride in the presence of anhydrous AICI₃ gives (C) of formula C₈H₈O. (C) on treatment with conc. nitric acid and conc. sulphuric acid gives (D) of formula C₈H₇NO₃. Identify A,BC,D,E and explain the reactions involved.
Answer:
1. (A) gives brisk effervescence with Na₂CO₃ solution and it must be a carboxylic acid. (A) gives brisk effervescence with NNa₂CO₃ solution and it must be a carboxylic acid. (A) is C₆H₅COOH benzoic acid.

2. Sodium salt of benzoic acid on reaction with sodalime (decarboxylation) produces benzene as (B)

3. Benzene on treatment with acetyl chloride in the presence of anhydrous AlCl₃ gives acetophenone as (C)

4. Acetophenonc on reaction with conc. HNO₃ and cone. H₂SO₄ gives m – nitro acetophenone as (D)

Question 30.
An organic compound (A) of molecular formula C₂H₆O on reaction with acidified K₂Cr₂O₇ gives (B) of molecular formula C₂H₄O which on further oxidation gives (C) of molecular formula C₂H₄O₂. Compound (C) reacts with (A) in the presence of conc. H₂SO₄ gives (D) of molecular formula C₄H₈O₂. Identify A,B,C,D and explain the reaction Involved.
Answer:
1. An organic compound (A) of molecular formula C₂H₆O is identified as ethanol.

2. Ethanol on oxidation with acidified K₂Cr₂O₇ gives first acetaldehyde as (B) which on further oxidation gives acetic acid as (C)

3. Ethanol reacts with acetic acid in the presence of conc. H₂SO₄, esterification take place to give ethyl acetate as product (D)

Question 31.
An organic compound (A) of molecular formula C₂H₄O₂ gives brisk effervescence with Na₂CO₃. Acetyl chloride reacts with sodium acetate to give C₄H₆O₃ as (B). (B) on reaction with PCI₅ gives (C) of formula C₂H₁₀CI. (C) on reaction with ammonia gives (D) of molecular formula C₂H₅NO. Identify A,B,C,D and explain the reactions involved.
Answer:
1. Compound (A) gives brisk effervescence with Na₂CO₃ and so it must be a carboxylic acid. CH₃COOH (acetic acid) is compound A.

2. Acetyl chloride on heating with sodium acetate to give acetic anhydride as (B)

3. Acetic anhydride reacts with PCI₅ to give acetyl chloride CH₃COCI as (C)

4. Acetyl chloride on treatment with ammonia gives acetamide as (D)

Question 32.
An organic compound (A) of molecular formula C₂H₄O₂ reacts with PCI₅ to give (B) of formula C₂H₃OCI. (B) on treatment with ammonia gives (C) of formula C₂H₅NO. (C) on reaction with Br₂ and KOH gives CH₅N as (D). Identify A,B,C,D and explain the reactions involved.
Answer:
1. The organic compound (A) is identified as CH₃COOH (Acetic acid).

2. Acetic acid reacts with PCI₅ to form acetyl chloride as (B)

3. Acetyl chloride on reaction with ammonia gives acetamide as (C)

4. Acetamide on treatment with Br₂, and KOH gives methylamine as (D)

Question 33.
An organic compound (A) of molecular formula C₂H₅NO on treatment with LiAIH₄ gives (B) of formula C₂H₇N. (A) on treatment with Br₂ and excess of caustic alkali gives (C) of formula CH₅N. (A) on treatment with phosphorous pentoxide gives (D) of molecular formula C₂H₃N Identify A,B,C,D and explain the reaclions involved.
Answer:
1. The organic compound (A) is identified as CH₃CONH₂ acetamide.

2. Acetamide on treatment with LiAlH₄ gives ethylamine as product (B)

3. Acetamide on reaction with Br₂ and caustic alkali gives methyl amine as (C)

4. Acetamide on treatment with P₂O₅ gives Aceto nitrile (or) methyl cyanide as (D)

Question 34.
An organic compound (A) of molecular formula C₂H₅NO on reaction with P₂O₅ gives C₂H₃N(B). (B) on hydrolysis gives (C) of formula C₂H₄O₂ (C) on reaction with LiMB₄ gives (D) formula C₂H₆O. Identify A,B,C,D and explain the reactions involved.
Answer:
1. (A) is identified as CH₃CONH₂ acetarnide.

2. Acetamide on reaction with P₂O₅ gives methyl cyanide as (B)

3. Methyl cyanide on acid hydrolysis gives acetic acid CH₃COOH as (C)

4. Acetic acid on reaction with LiAlH₄ gives ethanol as (D)

Errors

1. Aldehydes IUPAC names
2. Ketone – IUPAC name
3. Ozonolysis – easy way to remember the products. Students may feel difficult in writing equation
4. Clemmenson reduction and Wolf – Kishner reduction may get confused

Rectifications

1. The name should end with the word – al, HCHO – methanal, Aldehyde – Al, Alcohol – ol

2. The name should end with the word – one.  Propanone

3. By the either side of = bond, add one oxygen atom as products

4. The products are same, only catalyst are different

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