Category: Samacheer Kalvi Notes

Tamilnadu Samacheer Kalvi 12th Chemistry Notes Chapter 7 Chemical Kinetics Notes

Chemical kinetics – The word kinetics is derived from the Greek word “kinesis” meaning movement. Chemical kinetics is the study of the rate and the mechanism of chemical reactions, proceeding under given conditions of temperature, pressure, concentration etc.

Rate of chemical reaction – A rate is a change in a particular variable per unit time. In a chemical reaction, the change in the concentration of the species involved in a chemical reaction per unit time gives the rate of a reaction.
Rate = \(\frac{-[\text { Change in the concentration of the reactants }]}{[\text { Change in time }]}\)

Unit of the rate of a reaction:
Unit of rate = \(\frac{\text { unit of concentration }}{\text { unit of time }}\)

Concentration is expressed in number of moles per litre and time is expressed in seconds and therefore the unit of the rate of a reaction is mol L^-1s^-1

Average rate – It is obtained by dividing the change in concentration of any of the reactant or product by the time taken for the change.

Instantaneous rate of a reaction – The rate of a reaction at a particular moment of time is called the Instantaneous rate of a reaction.

Rate law – The expression in which reaction rate is given in term of molar concentration of the reactants with each term raised to some power, which may or may not be same as the stoichiometric coefficient of the reacting species in a balanced chemical equation.
For a general reaction, xA+yB → products

The rate law for the above reaction is generally expressed as Rate = k[A]^m [B]ⁿ
Where k is proportionality constant which is called rate constant. The values of m and n represent the reaction order with respect to A and B respectively.

Order of a reaction – The sum of exponents of the concentration of the reactants in the rate law expression.

Differences between rate and rate constant of a reaction

Elementary reaction – Each and every single step in a reaction mechanism is called an elementary reaction.

Molecularity – The total number of reactant species that are involved in an elementary step is called molecularity of that particular step.

Differences between order and Molecularity

Examples for the first order reaction

(i) Decomposition of dinitrogen pentoxide

(ii) Decomposition of thionylchloride;

(iii) Decomposition of the H202 in aqueous solution;

(iv) Isomerisation of cyclopropane to propene.

Pseudo first order reaction – A second order reaction can be altered to a first order reaction by taking one of the reactant in large excess. Such reaction is called pseudo first order reaction.

Examples for a zero order reaction
(i) Photochemical reaction between H₂ and Cl₂

(ii) Decomposition of N₂O on hot platinum surface

(iii) lodination of acetone in acid medium is zero order with respect to iodine.

Half life period of a reaction – The half life period of a reaction is defined as the time required for the reactant concentration to reach one half its initial value.

Collision theory – According to this theory, chemical reactions occur as a result of collisions between the reacting molecules.

Arrhenius equation

k= \(\mathrm{Ae}^{-\left(\frac{\mathrm{E}_{a}}{\mathrm{RT}}\right)}\)
A = Arrhenius factor (frequency factor)
R = Gas constant
k = Rate constant
E_a = Activation energy
T Absolute temperature (in K)

Factors affecting the reaction rate are,

1. Nature and state of the reactant
2. Concentration of the reactant
3. Surface area of the reactant
4. Temperature of the reaction
5. Presence of a catalyst

Samacheer Kalvi 12th Chemistry Notes

Tamilnadu Samacheer Kalvi 12th Chemistry Notes Chapter 6 Solid State Notes

Solids – The substances having definite shape mass and volume are called solids.

General characteristics of solids –

• Solids have definite volume and shape.
• Solids are rigid and incompressible
• Solids have strong cohesive forces.
• Solids have short inter atomic, ionic or molecular distances.
• Their constituents ( atoms , ions or molecules) have fixed positions and can only oscillate about their mean positions

Types of solids – They are two types.

1. Crystalline solids
2. Amorphous solids

Crystalline solids – In a crystalline solid, the particles are arranged in a regular and repetitive three dimensional arrangement.

Amorphous solids – In a amorphous solid, the particles are arranged in an irregular and non- repetitive three dimensional arrangement.

Isotropy – Isotropy means uniformity in all directions. In solid state isotropy means having identical values of physical properties such as refractive index electrical conductance etc., in all directions.

Anisotropy – Anisotropy is the property which depends on the direction of measurement.

Ionic solids – The structural units of an ionic crystal are cations and anions. They are bound together by strong electrostatic attractive forces. To maximize the attractive force, cations are surrounded by as many anions as possible and vice versa. Ex., NaCl crystal

Characteristics of ionic crystals

• Ionic solids have high melting points.
• These solids do not conduct electricity, because the ions are fixed in their lattice positions.
• They do conduct electricity in molten state (or) when dissolved in water because, the ions are free to move in the molten state or solution.
• They are hard as only strong external force can change the relative positions of ions.

Covalent solids – In covalent solids the constituents are bound together in a three dimensional network entirely by covalent bonds. Ex., Diamond

Molecular solids – In molecular solids, the constituents are neutral molecules. They are held together by weak vander waals forces. Ex., Naphthalene, solid CO₂, urea

Metallic solids – In metallic solids, the lattice points are occupied by positive metal ions and a cloud of electrons pervades the space. Ex., all kind of metals (Cu, Ni, Fe).

Crystal lattice – Crystalline solid is characterised by a definite orientation of atoms, ions or molecules, relative to one another in a three dimensional pattern. The regular arrangement of these species throughout the crystal is called a crystal lattice.

Unit Cell – A basic repeating structural unit of a crystalline solid is called a unit cell.

Primitive and non-primitive unit cell:

• A unit cell that contains only one lattice points is called a primitive unit cell, which is made up from the lattice points at each of the comers.
• In case of non-primitive unit cells there are additional lattice points, either on a face of the unit cell or with in the unit cell.

Seven classes of primitive crystal systems :

Packing efficiency – There is some free space between the spheres of a single layer and the spheres of successive layers. The percentage of total volume occupied by these constituent spheres gives the packing efficiency of an arrangement.

Schottky defect: – Schottky defect arises due to the missing of equal number of cations and anions from the crystal lattice. This effect does not change the stoichiometry of the crystal. Example :NaCl.

Frenkel defect: – Frenkel defect arises due to the dislocation of ions from its crystal lattice. The ion which is missing from the lattice point occupies an interstitial position.
Example: AgBr

Metal excess defect: – Metal excess defect arises due to the presence of more number of metal ions as compared to anions.Ex., Alkali halides (NaCl, KCl).

Metal deficiency defect: – Metal deficiency defect arises due to the presence of less number of cations than the anions. This defect is observed in a crystal in which, the cations have variable oxidation states. Example: FeO

Impurity defect: – This defect arises due to cation vacancies. In some ionic compounds presence of impurity produce some defects called impurity defects.
Ex, (i) presence of Cd⁺⁺ ion as impurity in AgCl.
(ii) presence of Sr⁺⁺ ion as impurity in AgCl.

Samacheer Kalvi 12th Chemistry Notes

Tamilnadu Samacheer Kalvi 12th Chemistry Notes Chapter 5 Coordination Chemistry Notes

Double Salts:

• Addition compounds are formed when stoichiometric amounts of two or more stable compounds combine together.
• The Compounds which exist only in the solid state but dissociate into their constituent simple ions when dissolved in water. Such addition compounds are called double salts.
• For example, Mohr’s Salt – FeSO₄.(NH₄)₂SO₄.6H₂O Potash alum – K₂SO₄.Al₂(SO₄)₃.24 H₂O

Coordination Compounds :

• The transition metals have a tendency to form complexes. The name is derived from the Latin words “complexus” and “coordinate” which mean “hold” and “to arrange” respectively.
• The compounds which retain their identity even in the solution, and have properties entirely different from those of the constituent simple ions are called coordination compounds.
• For example, [Cu(NH₃)₄]SO₄ is a typical coordination compound.

Coordination Entity :

Coordination entity is an ion or a neutral molecule, composed of a central atom, usually a metal and the array of other atoms or groups of atoms (ligands) that are attached to it. In the formula the coordination entity is enclosed in sequare brackets. For example, in potassium ferrocyanide, K₄[Fe(CN)₆], the coordination entity is [Fe(CN)₆]^4-

Central metal atom / ion :
The central atom/ion is the one that occupies the central position in a coordination entity and binds other atoms or groups of atoms (ligands) to itself, through a coordinate covalent bond. For example, in K₄[Fe(CN)₆] the central metal ion is Fe²⁺.

Ligands :
The ligands are the atoms or groups of atoms bound to the central atom/ion. The atom in a ligand that is bound directly to the central metal atom is known as a donor atom. For example, in K₄[Fe(CN)₆] the ligand is CN^– ion.

Coordination sphere :
The complex ion of the coordination compound containing the central metal atom/ion and the ligands attached to it, is collectively called coordination sphere and are usually enclosed in square brackets with the net charge. For example, the coordination compound K₄[Fe(CN)₆] contains the complex ion [Fe(CN)₆]^4- and is referred as the coordination sphere.

Coordination polyhedron :
The three dimensional spacial arrangement of ligand atoms/ ions that are directly attached to the central atom is known as the coordination polyhedron. For example, in K₄[Fe(CN)₆] the coordination polyhedra is octahedral. The coordination polyhedra of [Ni(CO)₄] is tetrahedral.

Coordination number :
The number of ligand donor atoms bonded to a central metal ion in a complex is called the coordination number of the metal. For example, in K₄[Fe(CN)₆] the coordination number of Fe²⁺ is 6.

Oxidation state :
The oxidation state of a central atom in a coordination entity is defined as the charge it would bear if all the ligands were removed along with the electron pairs that were shared with the central atom. For example, in the coordination entity [Fe(CN)₆]^4- the oxidation state of iron is represented as (II).

Types of complexes :
The coordination compounds can be classified into the following types based on,
(i) the net charge of the complex ion
(ii) kinds of ligands present in the coordination entity.

• Cationic complex : Carries a net positive charge. E.g: [Ag(NF₃)₂]^–
• Anionic complex : Carries a net negative charge. E.g: [Ag(CN)₂)]^–
• Neutral complex : Bears no net charge. E.g: [Ni(CO)₄].

Isomerism :
It is the phenomenon in which more than one coordination compounds having the same molecular formula have different physical and chemical properties due to different arrangement of ligands around the central metal atom.

Structural isomers :
The coordination compounds with same formula, but have different connections among their constituent atoms are called structural isomers or constitutional isomers.

Linkage isomers :
This type of isomers arises when an ambidentate ligand is bonded to the central metal atom/ion through either of its two different donor atoms.

Coordination isomers :
This type of isomers arises in the coordination compounds having both cation and anion as complex ions. The interchange of one or more ligands between the cationic and the anionic coordination entities result in different isomers.

Ionisation isomers :
This type of isomers arises when an ionisable counter ion itself can act as a ligand. The exchange of such counter ions with one or more ligands in the coordination entity will results in ionisation isomers.

Solvate isomers :
The exchange of free solvent molecules such as water, ammonia, alcohol etc. in the crystal lattice with a ligand in the coordination entity will give different isomers. These type of isomers are called solvate isomers.

Stereoisomers :
The stereoisomers of a coordination compound have the same chemical formula and connectivity between the central metal atom and the ligands. But they differ in the spatial arrangement of ligands in three dimensional space.

Geometrical isomers :
Geometrical isomerism exists in heteroleptic complexes due to different possible three dimensional spatial arrangements of the ligands around the central metal atom.

Optical isomerism :
Coordination compounds which possess chairality exhibit optical isomerism similar to organic compounds. The pair of two optically active isomers which are mirror images of each other are called enantiomers. Their solutions rotate the plane of the plane polarised light either clockwise or anti clockwise and the corresponding isomers are called’d’ (dextrorotatory) and T (levorotatory) forms respectively.

Homoleptic complex :
The central metal ion / atom is coordinated to only one kind of ligands is called a homoleptic complex. E.g: [Co(NH₃)₆]³⁺, [Fe(H₂O)₆]²⁺.

Heteroleptic complex :
The central metal ion/atom is coordinated to more than one kind of ligands is called a heteroleptic complex. E.g:[Co(NH₃)₅Cl]²⁺, [Pt(NH₃)Cl₂].
Crystal field splitting power of various ligands :

The above series is known as spectrochemical series.

Strong field ligands : The ligands present on the right side of the spectrochemical series such as carbonyl causes relatively larger crystal field splitting and are called strong field ligands.

Weak field ligands : The ligands present on the left side of the spectrochemical series such as iodide causes relatively smaller crystal fields splitting and are called weak fields ligands

Colour of the complex: Most of the transition metal complexes are coloured. A substance exhibits colour when it absorbs the light of a particular wavelength in the visible region and transmit the rest of the visible light. When this transmitted light enters our eye, our brain recognises its colour. The colour of the transmitted light is given by the complementary colour of the absorbed light.

Metallic carbonyls : Metal carbonyls are the transition metal complexes of carbon monoxide, containing metal-carbon bond. In these complexes CO molecule acts as a neutral ligand.

Synergic effect : In metal carbonyls, electron density moves from ligands to metal through sigma bonding and from metal to ligand through Pi-bonding. This is called synergic effect.

Labile complexes : In some cases, complexes can undergo rapid ligand substitution, such complexes are called labile complexes.

Inert complexes : In some cases, complexes undergo ligand substitution very slowly (or sometimes no substitution). Such complexes are called inert complexes.

Stability constant: The stability of a coordination complex is a measure of its resistance to the replacement of one ligand by another. The stability of a complex refer to the degree of association between two species involved in an equilibrium.

C is platin : It is a square planar coordination complex cis – [Pt(NH3)2Cl2], in which two similar ligands are in adjacent positions. It is a platinum based anticancer drug.

Coordination number : The number of ligand donor atoms bonded to central metal ion in a complex is called the coordination number of the metal.

Naming the central metal:

List of absorbed wavelength and their complementary colour

Samacheer Kalvi 12th Chemistry Notes

Tamilnadu Samacheer Kalvi 12th Chemistry Notes Chapter 4 Transition and Inner Transition Elements Notes

Position of d-block elements: Group – 3 to group – 12 of the modem periodic table is the position of d-block elements.

Electronic configuration: [Noble gas] (n – l)d^1-10 ns^1-2

Metallic behaviours: Except Cu, Ag, Au all are hard. Most of them are hexagonal close packed, cubic close packed (or) body centred cubic which are the characteristics of true metals.

Variation (or) trend in properties of d-block elements:

Standard electrode potentials: It is the value of the standard emf of a cell in which molecular hydrogen under standard pressure ( latm) and temperature (273K) is oxidised to solvated protons at the electrode.

Magnetic properties: Most of the compounds of transition elements are paramagnetic.

Magnetic moment: μ = \(g \sqrt{S(S+1)} \mu_{B}\)
where g = 2, S is the total spin quantum number of unpaired electrons and pB is Bohr Magneton.

Catalytic property: Most of the transition metals and their compounds act as catalyst.

Alloy formation: An alloy is formed by blending a metal with one or more other metals.

Formation of interstitial compounds: It is a compound that is formed when small atoms like hydrogen, boron, carbon or nitrogen are trapped in the interstitial holes in a metal lattice.

Formation of complex: Transition elements have a tendency to form complex compounds with a species that has an ability to donate an electron pair to form a coordinate covalent bond.

K₂Cr₂O₇: Potassium dichromate is an orange red crystalline solid.

Structure of dichromate ion:

Potassium permanganate -KMnO₄: It is a dark purple crystals.

Structure of permanganate ion:

Baeyer’s reagent: Cold, dilute alkaline KMnO₄

f-block elements: 1. Lanthanoids 2. Actinoids

Lanthanoids and Actinoids differences:

Samacheer Kalvi 12th Chemistry Notes 

Tamilnadu Samacheer Kalvi 12th Chemistry Notes Chapter 3 p-Block Elements-II Notes

Group-15 elements: About 78% of earth atmosphere contains dinitrogen gas. The other elements arsenic, antimony and bismuth are present as sulphides and are not very abundant.

Nitrogen:

• Nitrogen, the principle gas of atmosphere (78% by volume) is separated industrially from liquid air by fractional distillation.
• Nitrogen gas is rather inert.
• It can form complexes with metal.

Uses of nitrogen:

• Nitrogen is used for the manufacture of ammonia, nitric acid and calcium cyanamide etc.
• Liquid nitrogen is used for producing low temperature required in cryosurgery, and in biological preservation.

Ammonia:

• Ammonia is formed by the hydrolysis of urea.
• It is a pungent smelling gas and it is lighter than air.
• It is highly associated through strong hydrogen bonding.
• Ammonia act as a reducing agent.

Nitric acid:

• Nitric acid is prepared by heating equal amounts of potassium or sodium nitrate with concentrated H₂SO₄.
• Nitric acid act as an oxidising agent.
• Some metals such as Al, Fe, Co, Ni and Cr are rendered passive in concentrated nitric acid due to the formation of a layer of their oxides on the metal surface.

Uses of nitric acid:

• Nitric acid is used as a oxidising agent and in the preparation of aquaregia.
• Salts of nitric acid are used in photography (AgNO₃) and gunpowder for firearms. (NaNO₃)

Allotopic forms of phosphorus: Three forms namely,

• White phosphorous
• Red phosphorous
• Black phosphorous

Uses of phosphorous:

• The red phosphorus is used in the match boxes.
• It is also used for the production of certain alloys such as phosphor bronze.

Phosphine:

• Phosphine is the most important hydride of phosphorous.
• It is prepared by action of sodium hydroxide with white phosphorous.
• It is poisonous gas with rotten fish smell.

Uses of Phosphine: Phosphine is used for producing smoke screen as it gives large smoke. In a ship, a pierced container with a mixture of calcium carbide and calcium phosphide, liberates phosphine and acetylene when thrown into sea. The liberated phosphine catches fire and ignites acetylene. These burning gases serves as a signal to the approaching ships. This is known as Holmes signal.

Phosphorous trichloride:

• When a slow stream of chlorine is passed over white phosphorous, PCl₃ is formed.
• PCl₃ is used as a chlorinating agent and for the preparation of H₃PO₃.

Phosphorous petachloride:

• hen PCl₃ is treated with excess chlorine, PCl₅ is obtained.
• PCl₅ is chorinating agent and is useful for replacing hydroxyl groups by chlorine atom.

Groups-16 elements:

• Elements belonging group-16 are called chalgogens or ore forming elements.
• First element oxygen, the most abundant element, exists in both as dioxygen in air and in combined form as oxides.
• The other elements of this groups are, Sulphur, Selenium, Tellurium and Pollonium.

Oxygen:

• The atmosphere and water contain 23% and 83% by mass of oxygen respectively.
• The decomposition of hydrogen peroxide in the presence of catalyst produce oxygen.
• Under ordinary condition oxygen exists as a diatomic gas.
• Oxygen exists in two allotropic forms namely dioxygen (O₂) and ozone (O₃).

Uses of oxygen:

• Oxygen is one of the essential component for the survival of living organisms.
• It is used in welding (oxyacetylene welding)
• Liquid oxygen is used as fuel in rockets etc…

Allotrophic forms of sulphur: The crystallline allotropic forms are,

• Rhombic sulphur
• Monoclinic suphur

Amorphous allotropic forms are,

• Plastic sulphur
• Milk of sulphur
• Colloidal sulphur

Sulphur dioxide:

• Sulphur dioxide is prepared in the laboratory treating a metal or metal sulphite with sulphuric acid.
• Sulphur dioxide gas is formed in volcanic eruptions.
• It is an acidic oxide.
• It can be liquefied at 2.5 atomospheric pressure and 288 K temperature.

Uses of Sulphur dioxide:

• Sulphur dioxide is used in bleaching hair, silk, wool etc…
• It can be used for disinfecting crops and plants in agriculture.

Sulphuric acid:

• Sulphuric acid can be manufactured by lead chamber process or contact process.
• Pure sulphuric acid is a colourless,viscous liquid.
• It is highly reactive and it can act as dehydrating agent.

Uses of Sulphuric acid:

• Sulphuric acid is used in the manufacture of fertilisers, ammonium sulphate and super phosphates and other chemicals such as hydrochloric acid, nitric acid etc…
• It is used as a drying agent and also used in the preparation of pigments, explosives etc..

Group-17 elements:

• The halogens are present in combined form as they are highly reactive.
• They are also called as salt producers.
• The elements present in group-17 are, Fluorine, Chlorine, Bromine, Iodine and Astatine.

Chlorine:

• The main source of chlorine is sodiumchloride from sea water.
• Chlorine is highly reactive.
• Chlorine is manufactured by the electrolysis of brine in electrolytic process or by oxidation of HCl by air in Deacon’s process.
• It is a greenish yellow gas with pungent irritating odour.
• Bleaching powder is produced by passing chlorine gas through dry slaked time.

Uses of Chlorine:

• Purification of drinking water.
• Bleaching of cotton textiles, paper and rayon.
• It is used in extraction of gold and platinum.

Hydrochloric acid:

• It is prepared by the action,of sodium chloride and concentrated sulphuric acid.
• When three parts of cone. HCl and one part of cone. HNO₃ are mixed aquaregia (Royal water) is obtained.

Uses of Hydrochloric acid:

• Hydrochloric acid is used for the manufacture of chlorine, ammonium chloride, glucose from com starch etc.,
• It is used in the extraction of glue from bone and also for purification of bone black.

Hydrogen halides:

• Direct combination is a useful means of preparing hydrogen chloride. The reaction between hydrogen and fluorine is violent while the reaction between hydrogen and bromine or hydrogen and iodine are reversible and don’t produce pure forms.
• The hydrogen halides are extremely soluble in water due to the ionisation.
• Solution of hydrogen halides are acidic and known as hydrohalic acids.

Interhalogen compounds: Each halogen combines with other halogen to form a series of compounds called interhalogen compounds.

Group-18 elements:

• All the noble gases occur in the atmosphere.
• Elements belongs to group-18 are Helium, Neon, Argon, Krypton, Xenon and Radon.
• The first ionisation energy decreases from helium to radon.
• They are extremely stable and have a small tendency to gain or lose electrons.
• Noble gases are monoatomic.

Uses of Helium:

• Helium and oxygen mixture is used by divers in place of air oxygen mixture. This prevents the painful dangerous condition called bends.
• Helium is used to provide inert atmosphere in electric arc welding of metals.
• Helium has lowest boiling point hence used in cryogenics (low temperature science).
• It is much less denser than air and hence used for filling air balloons.

Uses of Neon: Neon is used in advertisement as neon sign and the brilliant red glow is caused by passing electric current through neon gas under low pressure.

Uses of Argon: Argon prevents the oxidation of hot filament and prolongs the life in filament bulbs

Uses of Krypton: Krypton is used in fluorescent bulbs, flash bulbs etc… Lamps filed with krypton are used in airports as approaching lights as they can penetrate through dense fog.

Uses of Xenon: Xenon is used in fluorescent bulbs, flash bulbs and lasers. Xenon emits an intense light in discharge tubes instantly. Due to this it is used in high speed electronic flash bulbs used by photographers.

Uses of Radon: Radon is radioactive and used as a source of gamma rays.Radon gas is sealed as small capsules and implanted in the body to destroy malignant i.e. cancer growth

Hydrogen halide

Samacheer Kalvi 12th Chemistry Notes

Tamilnadu Samacheer Kalvi 12th Chemistry Notes Chapter 1 Metallurgy Notes

Metallurgy: Metallurgy relates to the science and technology of metals. Metallurgy helps to study the various steps involved in the extraction of metal and the chemical principles behind these processes.

Mineral: A naturally occurring substance obtained by mining which contains the metal in free state or in the form of compounds like oxides, sulphides etc. is called a mineral.

Ore: Minerals that contains a high percentage of metal, from which it can be extracted conveniently and economically are called ores.

Gangue: Ores are associated with non-metallic impurities, rocky materials and siliceous matter which are collectively known as gangue.

Roasting: Roasting is the method, usually applied for the conversion of sulphide ores into their oxides. In this method, the concentrated ore is oxidized by heating it with excess of oxygen in a suitable furnace below the melting point of the metal.

Calcination: It is the process in which the concentrated ore is strongly heated in the absence of air. Here ore is converted into their oxides.

Smelting: It is the process of reducing the roasting metallic oxide to metal in molten condition.

Blistered copper: The solidified copper obtained after the reduction of copper matte has blistered appearance. This is called blistered copper.

Ellingham diagram: The graphical representation of variation of the standard Gibbs free energy of reaction for the formation of various metal oxides with temperature is called Ellingham diagram.

Distillation: In this method, the impure metal is heated to evaporate and the vapours are condensed to get pure metal.

Liquation: This method is employed to remove the impurities with high melting points from metals having relatively low melting points such as tin.

Electrolytic refining: The crude metal is refined by electrolysis. It is carried out in an electrolytic cell containing aqueous solution of the salts of the metal of interest. The rods of impure metal are used as anode and thin strips of pure metal are used as cathode.

Application of Aluminium (Al): Aluminium is the most abundant metal and is a good conductor of electricity and heat. It also resists corrosion. The following are some of its applications:

• Many heat exchangers/sinks and our day to day cooking vessels are made of aluminium.
• It is used as wraps (aluminium foils) and is used in packing materials for food items.
• Aluminium is not very strong, However, its alloys with copper, manganese, magnesium and silicon are light weight and strong and they are used in design of aeroplanes and other forms of transport.
• As Aluminium shows high resistance to corrosion, it is used in the design of chemical reactors, medical equipments, refrigeration units and gas pipelines.
• Aluminium is a good electrical conductor and cheap, hence used in electrical overhead and electric cables with steel core for strength.

Application of Zinc (Zn):

• Metallic zinc is used in galvanising metals such as iron and steel structures to protect them from rusting and corrosion.
• Zinc is also used to produce die-castings in the automobile, electrical and hardware industries.
• Zinc oxide is used in the manufacture of many products such as paints, rubber, cosmetics, pharmaceuticals, plastics, inks, batteries, textiles and electrical equipment. Zinc sulphide is used in making luminous paints, fluorescent lights and x-ray screens.
• Brass, an alloy of zinc is used in water valves and communication equipment, as it is highly resistant to corrosion.

Application of Iron (Fe):

• Iron is one of the most useful metals and its alloys are used everywhere including bridges, electricity pylons, bicycle chains, cutting tools and rifle barrels.
• Cast iron is used to make pipes, valves, pump stoves, etc.
• Magnets can be made of iron and its alloys and compounds.
• An important alloy of iron is stainless steel, and it is very resistant to corrosion. It is used in architecture, bearings, cutlery, surgical instruments and jewellery. Nickel steel is used for making cables, automobiles and aeroplane parts. Chrome steels are used for manufacturing cutting tools and crushing machines.

Application of Copper (Cu):

• Copper is the first metal used by the humans and extended use of its alloy bronze resulted in a new era, ’ Bronze age ’.
• Copper is used for making coins and ornaments along with gold and other metals.
• Copper and its alloys are used for making wires, water pipes and other electrical parts.

Application of Gold (Au):

• Gold, one of the expensive and precious metals. It is used for coinage, and has been used as standard for monetary systems in some countries.
• It is used extensively in j ewellery in its alloy form with copper. It is also used in electroplating to cover other metals with a thin layer of gold which are used in watches, artificial limb joints, cheap jewellery, dental fillings and electrical connectors.
• Gold nanoparticles are also used for increasing the efficiency of solar cells and also used as catalysts.

Samacheer Kalvi 12th Chemistry Notes

Tamilnadu Samacheer Kalvi 12th Computer Science Notes Chapter 6 Control Structures Notes

Control structure:
A program statement that causes a jump of control from one part of the program to another is called control structure or control statement.

Control Structures in Python:
There are three important control structures namely

• Sequential
• Alternative or Branching
• Iterative or Looping

Sequential Statement:
A sequential statement is composed of a sequence of statements which are executed one after another. A code to print your name, address and phone number is an example of sequential statement.

Alternative or branching statements in Python:
The types of alternative or branching statements provided by Python are:

• Simple if statement
• if..else statement
• if..elif statement

i) Simple if statement
Simple if is the simplest of all decision making statements. Condition should be in the form of relational or logical expression.

Syntax:
if:<condition>:
statements-block1

(ii) if..else statement
The if ..else statement provides control to check the true block as well as the false block. Following is the syntax of ‘if..else’ statement.

Syntax:
if:<condition>:
statements-block 1
else:
statements-block 2

iii) if..else statement
The if ..else statement provides control to check the true block as well as the false block. Following is the syntax of ‘if..else’ statement.

Syntax:
if:<condition>:
statements-block 1
else:
statements-block 2

Iteration or Looping constructs :

• Iteration or loop are used in situation when the user need to execute a block of code several of times or till the condition is satisfied.
• A loop statement allows to execute a statement or group of statements multiple times.

Looping constructs in Python:
Python provides two types of looping constructs:

• while loop
• for loop
  1. While loop:
  Syntax:
  while< condition > :
  statements block 1
  [else:
  statements block 2]

Samacheer Kalvi 12th Computer Science Notes

Tamilnadu Samacheer Kalvi 12th Computer Science Notes Chapter 7 Python Functions Notes

Function:
A named blocks of code that are designed to do one specific job is called
as Function.

Block in python:
A block is one or more lines of code, grouped together so that they are treated as one big sequence of statements while execution.

Main advantages of function:

• It avoids repetition and makes a high degree of code reusing.
• It provides better modularity for your application.

Recursive Function:
A Function which calls itself is called as Recursive Function.

Different types of function:

1. User-defined functions
2. Built in functions
3. Lambda functions
4. Recursive functions

1. User defined function:
Functions defined by the users themselves are called User defined functions.

Syntax:
def<function_name ([parameter 1, parameter 2 ]) > :
< Block of statement >
return < expression / None>

Example:
def welcome():
print(“Welcome to Python”)
return

2. Built-in functions:
Functions which are using Python libraries are called Built-in function.

Example:
print ()

3. Lambda function:

• Lambda function is mostly used for creating small and one-time anonymous function.
• Lambda functions are mainly used in combination with the functions like filterQ, map() and reduceQ.

Syntax of Lambda function (Anonymous Functions):
lambda [argument(s)]: expression

4. Recursive function:

• A recursive function calls itself. Imagine a process would iterate indefinitely if not stopped by some condition! Such a process is known as infinite iteration.
• The condition that is applied in any recursive function is known as a base condition.
• A base condition is must in every recursive function otherwise it will continue to execute like an infinite loop.

Scope of variable:

• Scope of variable refers to the part of the program, where it is accessible,
• The scope holds the current set of variables and their values.
• The two types of scopes are – local scope and global scope.

Local Scope:
A variable declared inside the function’s body or in the local scope is known as local variable.

Global scope:

• A variable, with global scope can be used anywhere in the program.
• It can be created by defining a variable outside the scope of any function or block.

Parameters and arguments:

• Parameters are the variables used in the function definition.
• Arguments are the values we pass to the function parameters.

Arguments Types:

• Arguments are used to call a function.
• There are primarily four types of functions namely :
  1. Required arguments
  2. Keyword arguments,
  3. Default arguments S Variable-length arguments

Required Arguments:

• “Required Arguments” are the arguments passed to a function in correct positional order.
• The number of arguments in the function call should match exactly with the function definition.
• Atleast one parameter to prevent syntax errors to get the required output.

Keyword Arguments:

• Keyword arguments will invoke the function after the parameters are recognized by their parameter names.
• The value of the keyword argument is matched with the parameter name and so, one can also put arguments in improper order (not in order).

Default Arguments:
In Python the default argument is an argument that takes a default value if no value is provided in the function call.

Variable-Length Arguments:

• In some instances it is needed to pass more arguments that have already been specified.
• These arguments are not specified in the function’s definition and an asterisk (*) is used to define such arguments.
• These types of arguments are called Variable-Length arguments.

Composition in functions:

• The value returned by a function may be used as an argument for another function in a nested manner is called

Samacheer Kalvi 12th Computer Science Notes

Tamilnadu Samacheer Kalvi 12th Computer Science Notes Chapter 5 Python -Variables and Operators Notes

Key features of Python:

• It is a general purpose programming language which can be, used for both scientific and non-scientific programming.
• It is a platform independent programming language.
• The programs written in Python are easily readable and understandable.

Python Coding:

• In Python, programs can be written in two ways namely Interactive mode and Script mode.
• The Interactive mode allows us to write codes in Python command prompt ( > > >) whereas in script mode programs can be written and stored as separate file with the extension . py and executed.
• Script mode is used to create and edit python source file.

Tokens.

• Python breaks each logical line into a sequence of elementary lexical components known as Tokens.
• The normal token types are
  1. Identifiers
  2. Keywords K
  3. Operators K
  4. Delimiters
  5. Literals

Operators used in Python :

• Arithmetic operators
• Relational or Comparative operator
• Logical operators
• Assignment operators
• Conditional operator

Input-output functions:

• The input () function helps to enter data at run time by the user .
• The output function print () is used to display the result of the program on the screen after execution.

Comment statement:
# are considered as comments and ignored by the Python interpreter.

Samacheer Kalvi 12th Computer Science Notes

Tamilnadu Samacheer Kalvi 12th Computer Science Notes Chapter 8 Strings and String Manipulations Notes

String:

• String is a data type in python, which is used to handle array of characters.
• String is a sequence of Unicode characters that may be a combination of letters, numbers, or special symbols enclosed within single, double or even triple quotes.

Slicing:

• Slice is a substring of a main string.
• A substring can be taken from the original string by using [ ] operator and index or subscript values.
• Thus, [ ] is also known as slicing operator.
• Using slice operator, we have to slice one or more substrings from a main string.

General format of slice operation: str[start:end]

• Start is the beginning index and end is the last index value of a character in the string.
• Python takes the end value less than one from the actual index specified.

Stride:

• Slice is a substring of a main string.
• Stride is a third argument in slicing operation which refers to the number of characters to move forward after the first character is retrieved from the string.

Function: center ()
center () returns a string with the original string centered to a total of width columns and filled with fillchar in columns that do not have characters.

Function: find ()

• The find () is used to search the first occurrence of the substring in the given string.
• It returns the index at which the substring starts.
• It returns -1 if the substring does not occur the string.

Function: lower ()
lower () returns the exact copy of the string with all the letters in lowercase

Function: islower()
islower () returns True if the string is in lowercase.

Function: upper()
upper () returns the exact copy of the string with all letters in uppercase

Function: isupper()
isupperQ returns True if the string is in uppercase.

Function: title()
title() returns a string in title case.

Function: capitalize ()
capitalize () is used to capitalize the first character of the string.

Function: swapcase ()
swapcase () will change case of every character to its opposite case vice-versa.

Function: format()

• The format( ) is used with strings is very versatile and powerful function used for formatting strings.
• The curly braces {}are used as placeholders or replacement fields which get replaced along with format() function.

Function: count()

• count( ) returns the number of substrings occurs within the given range.
• Substring may be a single character.

Function: isalnum ()

• isalnum () returns True if the string contains only letters and digit. It returns False.
• If the string contains any special character like _,@,#,*,etc.

Function: isalpha()
isalpha() returns True if the string contains only letters Otherwise return False.

Function: isdigit ()
isdigit () returns True if the string contains only numbers. Otherwise it returns False

Samacheer Kalvi 12th Computer Science Notes