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Tamilnadu Samacheer Kalvi 12th Chemistry Notes Chapter 12 Carbonyl Compounds Notes

Carbonyl compounds: An organic compounds, which contains is called carbonyl compounds. They plays an important role in the metabolic process. Carbonyl compounds are important constituents of fabrics, plastics and drugs.

Ozonolysis: Alkenes or Alkynes reacts with ozone to form ozonide which on subsequent cleavage with zinc and water gives corresponding aldehydes or ketones. This process is known as ozonolysis.

Hydration of alkynes: The hydration of alkynes in the presence of 40% dilute sulphuric acid and 1% H₂SO₄ to give the corresponding aldehydes or ketones.

Rosenmund reduction: 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.

Stephen’s reaction: When alkylcyanides are reduced using SnCl₂ / HCl, imines are formed, which on hydrolysis gives corresponding aldehyde. This reaction is called Stephen’s reaction.

Selective reduction of cyanides: Diisobutyl aluminium hydride (DIBAL -H) selectively reduces the alkyl cyanide to form imines which on hydrolysis gives aldehydes.

Etard reaction: When chromylchloride is used as an oxidising agent, toluene gives benzaldehyde. This reaction is called Etard reaction.

Gattermann – Koch reaction: In this reaction, carbon monoxide and HC1 generate formyl cation intermediate, which attacks the aromatic ring to form corresponding aldehydes.

Urotropine: Formaldehyde reacts with ammonia to form hexa methylene tetramine, which is also known as Urotropine.

Carbonyl compounds: An organic compounds, which contains c is called carbonyl compounds. They plays an important role in the metabolic process. Carbonyl compounds are important constituents of fabrics, plastics and drugs.

Ozonolysis: Alkenes or Alkynes reacts with ozone to form ozonide which on subsequent cleavage with zinc and water gives corresponding aldehydes or ketones. This process is known as ozonolysis.

Hydration of alkynes: The hydration of alkynes in the presence of 40% dilute sulphuric acid and 1% H₂SO₄ to give the corresponding aldehydes or ketones.

Rosenmund reduction: 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.

Stephen’s reaction: When alkylcyanides are reduced using SnCl₂ / HCl, imines are formed, which on hydrolysis gives corresponding aldehyde. This reaction is called Stephen’s reaction.

Selective reduction of cyanides: Diisobutyl aluminium hydride (DIBAL -H) selectively reduces the alkyl cyanide to form imines which on hydrolysis gives aldehydes.

Etard reaction: When chromylchloride is used as an oxidising agent, toluene gives benzaldehyde. This reaction is called Etard reaction.

Gattermann – Koch reaction: In this reaction, carbon monoxide and HCl generate formyl cation intermediate, which attacks the aromatic ring to form corresponding aldehydes.

Urotropine: Formaldehyde reacts with ammonia to form hexa methylene tetramine, which is also known as Urotropine.

Uses of Urotropine:

• Urotropine is used as a medicine to treat urinary infection.
• Nitration of Urotropine under controlled condition gives an explosive RDX (Research and development explosive). It is also called cyclonite or cyclotri methylene trinitramine.

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.

Clemmensen reduction: Aldehydes and Ketones when heated with zinc amalgam and concentrated hydrochloric acid gives hydrocarbons. This reduction is called Clemmensen reduction.

Wolf – Kishner reduction: Aldehydes and Ketones when heated with hydrazine and sodium ethoxide, hydrocarbons are formed. This reduction is called Wolf – Kishner reduction.

Aldol condensation: In the presence of bases like NaOH, or KOH, two molecules of an aldehyde or ketone having α – hydrogen add together to give (β- hydroxyl aldehyde (aldol) or β – hydroxyl ketone (ketol). This reaction is called aldol condensation reaction.

Crossed aldol condensation: Aldol condensation can also take place between two different aldehydes or ketones or between one aldehyde and one ketone such an aldol condensation is called crossed aldol condensation.

Claisen – Schmidt Condensation: Benzaldehyde condenses with aliphatic or methyl ketone in the presence of dil. alkali at room temperature to form unsaturated aldehyde or ketone. This type of reaction is called Claisen – Schmidt condensation.

Cannizaro reaction: In the presence of concentrated aqueous alkali, aldehydes which do not have a – hydrogen atom under of self oxidation and reduction to give a mixture of alcohol and a salt of carboxylic acid. This reaction is called Cannizaro reaction.

Crossed Cannizaro reaction: When Cannizaro reaction takes place between two different aldehydes (neither containing an a – hydrogen atom), the reaction is called as cross cannizaro reaction.

Benzoin condensation: This reaction involves the treatment of an aromatic aldehyde with alcoholic KCN. The products are hydroxyl ketone.

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 a, p unsaturated acid is obtained. This reaction is known as Perkin’s reaction.

Knoevenagal reaction: Benzaldehyde condenses with malonic acid in the presence of pyridine forming cinnamic acid is called Knoevenagal reaction or condensation.

Schiff’s base: Aromatic aldehydes react with primary amines in the presence of an acid to form schiff’s base.

Tollens Reagent Test: Tollens reagent is an ammonical silver nitrate solution. When an aldehyde is warmed with Tollens reagent a bright silver mirror is produced due to the formation of silver metal. This reaction is also called silver mirror test for aldehydes.

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.

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

Schiffs’ reagent Test: Dilute solution of aldehydes when added to schiffs’ reagent (Rosaniline hydrochloride dissolved in water and its red colour decolourised by passing S02) yields its red colour. This is known as Schiffs’ test for aldehydes. Ketones do not give this test. Acetone however gives a positive test but slowly.

Formalin: 40% aqueous solution of formaldehyde is called formalin. It is used for preserving biological specimens

Uses of Acetaldehyde:

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

Uses of Acetone:

• Acetone is used as a solvent, in the manufacture of smokeless powder (cordite).
• It is used as a nail polish remover.
• It is used in the preparation of sulphonal, a hypnotic.
• It is used in the manufacture of thermosoftening plastic Perspex.

Uses of Benzaldehyde:

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

Uses of Aromatic Ketones:

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

Carboxylic acids: An organic compounds containing a carboxylic functional group, – COOH are called carboxylic acids. The Carboxyl group is the combination of carbonyl group and the hydroxyl group.

Vinegar: It is a 6% to 8% solution of acetic acid in water.

Glacial acetic acid: 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, it 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.

Esterification: When carboxylic acids are heated with alcohols in the presence of cone. H₂SO₄ or dry HCl gas esters are formed. The reaction is reversible and is called esterification.

Decarboxylation: Removal of CO₂ from carboxyl group is called as decarboxylation. Carboxylic acids lose carbon-di-oxide to form hydro carbon when their sodium salts are heated with soda lime (NaOH and CaO in the ratio 3:1)

Kolbe’s electrolytic reaction: The aqueous solutions of sodium or potassium salts of carboxylic acid on electrolysis gives alkanes at anode. This reaction is called kolbes electrolysis.

Hell – Volhard – Zelinsky reaction: Carboxylic acids having an a – hydrogen are
halogenated at the α – position on treatment with Cl₂ or Br₂ in the presence of small amount of red phosphorus to form α – halo carboxylic acids. This reaction is known as  Hell – Volhard – Zelinsky reaction (HVZ reaction)

Tests for carboxylic acid group:

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

Functional derivatives of carboxylic acids: Compounds such as acid chlorides,amides,esters etc., are called carboxylic acid derivatives because they differ from a carboxylic acid only in the nature of the group or atom that has replaced the – OH group of carboxylic acid.

Relative reactivity of Acid derivatives: The reactivity of the acid derivatives follows the

Order of reactivity of the acid derivatives with nucleophilic reagent follows the order:
Acid halide > acid anhydride > esters > acid amides

Transesterification: Ester of an alcohol can react with another 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.

Ammonolysis: Esters react slowly with ammonia to form amides and alcohol. This reaction is called ammonolysis.

Claisen Condensation: Esters containing at least one a – hydrogen atom undergo self condensation in the presence of a strong base such as sodium ethoxide to form P – keto ester

Hoff mann’s degradation reaction: Amides reacts with bromine in the presence of caustic potash (KOH) to form a primary amine carrying one carbon less than the parent amide. This is called Hoff mann’s degradation reaction.

Uses of Formic acid:

• For the dehydration of hides
• As a coagulating agent for rubber latex
• In medicine for treatment of gout
• As an antiseptic in the preservation of fruit juice

Uses of Acetic acid:

• As table vinegar
• For coagulating rubber latex
• For manufacture of cellulose acetate and poly vinylacetate

Uses of Benzoic acid:

• As food preservative either in the pure form or in the form of sodium benzoate
• In medicine as an urinary antiseptic
• For manufacture of dyes

Uses of Acetyl chloride:

• As acetylating agent in organic synthesis
• In detection and estimation of – OH, – NH₂ groups in organic compounds

Uses of Acetic anhydride:

• Acetylating agent
• In the preparation of medicine like asprin and phenacetin
• For the manufacture plastics like cellulose acetate and poly vinyl acetate.

Uses of Ethyl acetate:

• In the preparation of artificial fruit essences
• As a solvent for lacquers.
• In the preparation of organic synthetic reagent like ethyl acetoacetate.

Uses of Acetamide: Acetamide is used in the preparation of Primary amines.

Flavours of some of the esters are given below:

Samacheer Kalvi 12th Chemistry Notes

Tamilnadu Samacheer Kalvi 12th Chemistry Notes Chapter 13 Organic Nitrogen Compounds Notes

Nitro Compounds: If one of the hydrogen atom of hydrocarbon is replaced by the -NO-, group, the resultant organic compound is called nitro compound.

Tautomerism: 1° and 2° nitroalkanes, having a-H , also show as equilibrium mixture of two tautomers namely nitro and aci form. Such a isomeric form are collectively called tautomerism.

Nature of Nitro form:

• Less acidic
• Dissolves in NaOH slowly
• Decolourises FeCl₃ solution
• Electrical conductivity is low

Nature of aci form:

• More acidic and also called pseudoacids (or) nitronic acids
• Dissolves in NaOH instantly
• With FeCl₃ gives reddish brown colour
• Electrical conductivity is high

Nef carbonyl synthesis: Nitro alkanes are reacts with potassium hydroxide, followed by hydrolysis they form corresponding aldehyde.

Amine: An organic compound, which containing NH, functional group and they are called amines.

Mendius reaction: The reduction of alkyl or aryl cyanides reaction in which Na / C₂H₅OH is used as a reducing agent is called Mendius reaction.

Hoffmann’s degradation reaction: When Amides are treated with bromine in the presence of aqueous or ethanolic solution of KOH, primary amines with one carbon atom less than the parent amides are obtained.

Gabriel phthalimide synthesis: Gabriel synthesis is used for the preparation of Aliphatic primary amines. Phthalimide on treatment with ethanolic KOH forms potassium salt of phthalimide which on heating with alkyl halide followed by alkaline hydrolysis gives primary amine.

Hoffmann’s ammonolysis: When Alkyl halides (or) benzylhalides are heated with alcoholic ammonia in a sealed tube, mixtures of 1°, 2° and 3° amines and quaternary ammonium salts are obtained.

The boiling point of various amines follows the order,

Order of basic strength in case of alkyl substituted amines in aqueous solution is,

The relative basicity of amines follows the below mentioned order
Alkyl amines > Aralkyl amines > Ammonia > N – Aralkyl amines > Aryl amines

Schotten – Baumann reaction: Aniline reacts with benzoylchloride in the presence of NaOH to give N – phenyl benzamide. This reaction is known as Schotten – Baumann reaction.

Libermann’s nitroso test: Alkyl and aryl secondary amines react with nitrous acid to give N – nitroso amine as yellow oily liquid which is insoluble in water. This reaction is known as Libermann’s nitroso test.

Carbylamine reaction: Aliphatic (or) aromatic primary (only) amines react with chloroform and alcoholic KOH to give isocyanides (carbylamines), which has an unpleasant smell. This reaction is known as carbylamines test.

Mustard oil reaction: When primary amines are treated with carbon disulphide, N – alkyldithio carbonic acid is formed which on subsequent treatment with HgCl2, give an alkyl isothiocyanate.

Diazonium Salts: Aromatic amines on treatment with NaN02 and HC1 gives diazonium salts. They are stable only for a short time.

Sandmeyer reaction: On mixing freshly prepared solution of benzene diazonium chloride with cuprous halides, aryl halides are obtained. This reaction is called Sandmeyer reaction.

Gattermann reaction: Conversion of benzene diazonium chloride into chloro / bromo arenes can also be effected using HC1 or HBr and copper powder. This reaction is called Gattermann reaction.

Baltz – schiemann reaction: When benzene diazonium chloride is treated with fluoroboric acid, benzene diazonium tetra fluoroborate is precipitated which on heating decomposes to give fluorobenzene.

Gomberg reaction: Benzene diazonium chloride in the presence of sodium hydroxide to give
biphenyl. This reaction in known as the Gomberg reaction. , .

Coupling reactions: Benzene diazonium chloride reacts with electron rich aromatic compounds like phenol, aniline to form brightly coloured azo compounds. Coupling generally occurs at the para position. If para position is occupied then coupling occurs at the ortho position.

Thrope nitrile condensation: Self condensation of two molecules of alkyl nitrile (containing a-H atom) in the presence of sodium to form iminonitrile.

Levine and hauser acetylation: The nitriles containing a – hydrogen also undergo condensation with esters in the presence of sodamide in ether to form ketonitriles. This reaction is known as “ Levine and hauser” acetylation.

Cyanomethylation reaction: This reaction involves replacement of ethoxy (OC₂H₅) group by methylnitrile (-CH₂ CN) group and it is called as cyanomethylation reaction.

Uses of nitroalkanes:

• Nitromethane is used as a fuel for cars
• Chloropicrin (CCl₃ NO₂) is used as an insecticide
• Nitroethane is used as a fuel additive and precursor to explosive and they are good solvents for polymers, cellulose ester, synthetic rubber and dyes etc.,
• 4% solution of ethylnitrite in alcohol is known as sweet spirit of nitre and in used as diuretic.

Uses of nitrobenzene:

• Nitrobenzene is used to produce lubricating oils in motors and machinery
• It is used in the manufacture of dyes, drugs, pesticides, synthelic rubber, aniline and explosives like TNT, TNB.

Uses of cyanides and isocyanides:

• Alkyl cyanides are important intermediates in the organic synthesis of larger number of compounds like acids, amides, esters, amines etc.
• Nitriles are used in textile industry in the manufacture of nitrile rubber and also as a solvent particularly in perfume industry.

Cancer Drug: Mitomycin C, and anticancer agent used to treat stomach and colon cancer, contains an aziridine ring. The aziridine functional group participates in the drug’s degradation by DNA, resulting in the death of cancerous cells.

Samacheer Kalvi 12th Chemistry Notes

Tamilnadu Samacheer Kalvi 12th Chemistry Notes Chapter 14 Biomolecules Notes

Bio chemistry: The field of studying about the chemistry behind the biological processes is called bio chemistry.

Carbohydrates: Carbohydrates are the most abundant organic compounds in every living organism. They are also known as saccharides. In general carbohydrates are hydrates of carbon, containing hydrogen and oxygen in the same ratio as in water. They are also defined as polyhydroxy aldehydes or ketones.

Dextro rotatory: Dextro rotatory compounds rotate the plane of plane polarised light in clockwise direction. Dextro rotatory compounds are represented as D – (+).

Levo rotatory: Levo rotatory compounds rotate the plane of plane polarised light is anticlockwise direction. Levo rotatory compounds are represented as L – (-).

Monosaccharides: Monosaccharides are carbohydrates that cannot be hydrolysed further and are also called simple sugars. Monosaccharides have general formula Cn(H20)n. While there are many monosaccharides known only about 20 of them occur in nature. Some common examples are glucose, fructose, ribose, erythrose.

Glucose: It is a simple sugar. It is present in honey, sweet fruits such as grapes and mangoes etc therefore glucose is also called as grape sugar. Human blood contains about lOOmg/dL of glucose.

Anomers: The conversion of the achiral aldehyde carbon into a chiral one leading the possibility two isomers. These two isomers differ only in the configuration of Cj – carbon. These isomers are called anomers.

Mutarotation: The slow interconversion of a – D glucose and p – D glucose via open chain form untill equilibrium is established giving constant specific rotation (+53°). This phenomenon is called mutarotation.

Epimerisation: Sugar differing in configuration at an asymmetric centre is known as epimers. The process by which one epimer is converted into other is called epimerisation.

Bio chemistry: The field of studying about the chemistry behind the biological processes is called bio chemistry.

Carbohydrates: Carbohydrates are the most abundant organic compounds in every living organism. They are also known as saccharides. In general carbohydrates are hydrates of carbon, containing hydrogen and oxygen in the same ratio as in water. They are also defined as polyhydroxy aldehydes or ketones.

Dextro rotatory: Dextro rotatory compounds rotate the plane of plane polarised light in clockwise direction. Dextro rotatory compounds are represented as D – (+).

Levo rotatory: Levo rotatory compounds rotate the plane of plane polarised light is anticlockwise direction. Levo rotatory compounds are represented as L – (-).

Monosaccharides: Monosaccharides are carbohydrates that cannot be hydrolysed further and are also called simple sugars. Monosaccharides have general formula Cn(H20)n. While there are many monosaccharides known only about 20 of them occur in nature. Some common examples are glucose, fructose, ribose, erythrose.

Glucose: It is a simple sugar. It is present in honey, sweet fruits such as grapes and mangoes etc therefore glucose is also called as grape sugar. Human blood contains about lOOmg/dL of glucose.

Anomers: The conversion of the achiral aldehyde carbon into a chiral one leading the possibility two isomers. These two isomers differ only in the configuration of Cj – carbon. These isomers are called anomers.

Mutarotation: The slow interconversion of a – D glucose and p – D glucose via open chain form untill equilibrium is established giving constant specific rotation (+53°). This phenomenon is called mutarotation.

Epimerisation: Sugar differing in configuration at an asymmetric centre is known as epimers. The process by which one epimer is converted into other is called epimerisation.

Bio chemistry: The field of studying about the chemistry behind the biological processes is called bio chemistry.

Carbohydrates: Carbohydrates are the most abundant organic compounds in every living organism. They are also known as saccharides. In general carbohydrates are hydrates of carbon, containing hydrogen and oxygen in the same ratio as in water. They are also defined as polyhydroxy aldehydes or ketones.

Dextro rotatory: Dextro rotatory compounds rotate the plane of plane polarised light in clockwise direction. Dextro rotatory compounds are represented as D – (+).

Levo rotatory: Levo rotatory compounds rotate the plane of plane polarised light is anticlockwise direction. Levo rotatory compounds are represented as L – (-).

Monosaccharides: Monosaccharides are carbohydrates that cannot be hydrolysed further and are also called simple sugars. Monosaccharides have general formula Cn(H20)n. While there are many monosaccharides known only about 20 of them occur in nature. Some common examples are glucose, fructose, ribose, erythrose.

Glucose: It is a simple sugar. It is present in honey, sweet fruits such as grapes and mangoes etc therefore glucose is also called as grape sugar. Human blood contains about lOOmg/dL of glucose.

Anomers: The conversion of the achiral aldehyde carbon into a chiral one leading the possibility two isomers. These two isomers differ only in the configuration of Cj – carbon. These isomers are called anomers.

Mutarotation: The slow interconversion of a – D glucose and p – D glucose via open chain form untill equilibrium is established giving constant specific rotation (+53°). This phenomenon is called mutarotation.

Epimerisation: Sugar differing in configuration at an asymmetric centre is known as epimers. The process by which one epimer is converted into other is called epimerisation.

Fructose: Fructose is another commonly known monosaccharide having the same molecular formula as glucose. It is laevorotatory and a ketohexose. It is present abundantly in fruits and hence it is also called as fruit sugar.

Disaccharides: They are sugars that yield two molecules of monosaccharides on hydrolysis. This reaction is usually catalysed by dilute acid or enzyme. In disaccharides two monosaccharides are linked by oxide linkage called glycosidic linkage.

Invert sugar: During hydrolysis of sucrose the optical rotation of the reaction mixture changes from dextro to levo. Hence, sucrose is also called invert sugar.

Polysaccharides: Polysaccharides consist of large number of monosaccharide units bonded together by glycosidic bonds and are the most common form of carbohydrates. Since, they do not have sweet taste polysaccharides are called as non-sugars. They form linear and branched chain molecules.

Starch: Starch is used for energy storage in plants. Potatoes, com, wheat and rice are the rich sources of starch. It is a polymer of glucose in which glucose molecules are lined by a(l,4) glycosidic bonds. Starch can be separated into two fractions namely, water soluble amylose and water insoluble amylopectin. Starch contains about 20 % of amylase and about 80% of amylocpectin.

Cellulose : Cellulose is the major constituent of plant cell walls. Cotton is almost pure cellulose. On hydrolysis cellulose yields D-glucose molecules. Cellulose is a straight chain polysaccharide. The glucose molecules are linked by P(l,4) glycosidic bond.

Glycogen: Glycogen is the storage polysaccharide of animals. It is present in the liver and muscles of animals. Glycogen is also called as animal starch. On hydrolysis it gives glucose molecules.

Importance of carbohydrates:

1. Carbohydrates, widely distributed in plants and animals, acts mainly as energy sources and structural polymers.
2. Carbohydrate is stored in the body as glycogen and in plant as starch.
3. Carbohydrates such as cellulose which is the primary components of plant cell wall, is used to make paper, furniture (wood) and cloths (cotton)
4. Simple sugar glucose serves as an instant source of energy.
5. Ribose sugars are one of the components of nucleic acids.
6. Modified carbohydrates such as hyaluronate (glycosaminoglycans) act as shock absorber and lubricant.

Proteins: Proteins are most abundant biomolecules in all living organisms. The term protein is derived from Greek word “proteious” meaning primary or holding first place.

Amino acids: Amino acids are compounds which contain an amino group and a carboxylic acid group.

Isoelectric point: At a specific pH value the net charge of an amino acid is neutral is called isoelectric point.

Peptide bond: The carboxyl group of the first amino acid react with the amino group of the second amino acid to give an amide linkage between these amino acids. This amide linkage is called peptide bond.

Denaturation: The process of protein losing its higher order structure without losing the primary structure is called denaturation.

Importance of proteins:

1. All biochemical reactions occur in the living systems are catalysed by the catalytic proteins called enzymes.
2. Proteins such as keratin, collagen acts as structural back bones.
3. Proteins are used for transporting molecules (Haemoglobin), organelles (Kinesins) in the cell and control the movement of molecules in and out of the cells (Transporters). ‘
4. Antibodies help the body to fight various diseases
5. Proteins are used as messengers to coordinate many functions. Insulin & glucagon controls the glucose level in the blood.
6. Proteins act as receptors that detect presence of certain signal molecules and activate the proper response.
7. Proteins are also used to store metals such as iron (Ferritin) etc.

Enzymes: There are many biochemical reactions that occur in our living cells. Digestion of food and harvesting the energy from them, and synthesis of necessary molecules required for various cellular functions are examples for such reactions. All these reactions are catalysed by special proteins called enzymes.

Lipids: They are organic molecules that are soluble in organic solvents such as chloroform and methanol and are insoluble in water. The word lipid is derived from the Greek word ‘lipos’ meaning fat.

Biological importance of lipids:

1. Lipids are the integral component of cell membrane. They are necessary of structural integrity of the cell.
2. The main function of triglycerides in animals is as an energy reserve. They yield more energy than carbohydrates and proteins.
3. They act as protective coating in aquatic organisms.
4. Lipids of connective tissue give protection to internal organs.
5. Lipids help in the absorption and transport of fat soluble vitamins.
6. They are essential for activation of enzymes such as lipases.
7. Lipids act as emulsifier in fat metabolism.

Vitamins: Vitamins are small organic compounds that cannot be synthesised by our body but are essential for certain function.

Fat soluble vitamins: These vitamins absorbed best when taken with fatty food and are stored in fatty tissues and livers. These vitamins do not dissolve in water. Hence they are called fat soluble vitamins. Vitamin A, D, E & K are fat-soluble vitamins.

Water soluble vitamins: Vitamins B and C are readily soluble in water.

Nucleic acids: The inherent characteristics of each and every species are transmitted from one generation to the next. It has been observed that the particles in nucleus of the cell are responsible for the transmission of these characteristics. They are called chromosomes and are made up of proteins and another type of biomolecules called nucleic acids.

Nucleosides and nucleotides: The molecule without the phosphate group (molecule consists of sugar and base only) is called a nucleosides. A nucleotide is derived from a nucleoside by the addition of a molecule of phosphoric acid or phosphate unit.

Types of RNA molecules: RNA molecules are classified according to their structure and function into three major types,

1. Ribosomal RNA (r-RNA)
2. Messenger RNA (m-RNA)
3. Transfer RNA (t-RNA) ‘

DNA finger printing: One of the most accurate methods for placing an individual at the scene of a crime has been a fingerprint. With the advent of recombinant DNA technology, a more powerful tool is now available is called DNA finger printing.

Hormones: Hormone is an organic substance that is secreted by one tissue into the blood system and induces a physiological response in other tissues. It is an intercellular signalling molecule.

Samacheer Kalvi 12th Chemistry Notes

Tamilnadu Samacheer Kalvi 12th Chemistry Notes Chapter 15 Chemistry in Everyday Life Notes

Drug: The word drug is derived from the French word “drogue” meaning “dry herb”. A drug is a substance that is used to modify or explore physiological systems or pathological states for the benefit of the recipient. It is used for the purpose of diagnosis, prevention, cure / relief of a disease.

Drug targets: The drug molecule interacts with biomolecules such as enzymes, receptors etc., which are refered as drug targets.

Antagonists: A drug that binds to the receptor site should inhibit its natural function. Such drugs are called antagonists.

Agonists: A drug which mimic the natural messenger by switching on the receptor. These types of drugs are called agonists.

Tranquilizers: They are neurologically active drugs. They acts on the central nervous system by blocking the neuro transmitter dopamine in the brain.

Analgesics: Analgesics are the compounds which relieve all sorts of pains without the loss of consciousness. These are also called pain killer or pain relievers.

Antipyretics: Antipyretics are the compounds which are used for the purpose of reducing fever (lowering the body temperature to the normal)

Anaesthetics: The drugs which produce loss of sensation are called anaesthetics. They are two types (i) General anaesthetics and (it) Local anaesthetics.

Antacids: Certain drugs provide relief from burning sensation. These are known as antacids.

Antihistamines: The drugs which interfere with the natural action of histamines and prevent the allergic reaction.

Antimicrobials: They tend to prevent or destroy or inhibit the pathogenic action of microbes such as bacteria, viruses, fungi etc.

Antiseptics: Drug which either kill or inhibit the growth of micro organisms.

Antifertility drugs: These are the chemical substances used to control pregnancy. They are also called contraceptives or birth control pills.

Food additives: The substances which are not naturally a part of the food and added to improve the quality of the food are called food additives.

Advantages of food additives: (i) Uses of preservatives reduce the product spoilage and extend the shelf-life of food, (ii) Addition of vitamins and minerals reduces the mall nutrient, (iii) Flavouring agents enhance the aroma of the food.(iv) Antioxidants prevent the formation of potentially toxic oxidation products of lipids and other food constituents.

Preservatives: Preservatives are capable of inhibiting retarding or arresting the process of fermentation acidification or other decomposition of food by growth of mirco organisms.

Antioxidants: Antioxidants are substances which retard the oxidative deteriorations of food.

Sugar substituents: Those compounds that are used like sugars for sweetening, but are metabolised without the influence of insulin are called sugar substituents.

Artificial sweetening agents: Synthetic compounds which imprint a sweet sensation and possess no or negligible nutritional value are called artificial sweeteners.

Soaps: Sodium or potassium salt of a long chain fatty acid is called a soap.

Total fatty matter: It is defined as the total amount of fatty matter that can be separated from a sample after splitting with mineral acids. Higher the TFM quantity in the soap better is its quality.

Detergents: Synthetic detergents are formulated products containing either sodium salts of alkyl hydrogen sulphates or sodium salts of long chain alkyl benzene sulphuric acids.

Polymers: They are macromolecules of high molecular masses formed by combination of a large number of simple molecules.

Addition polymers: In these polymers, monomer units are added to form long chains without the elimination of any by product.

Condensation polymers: In these polymers, monomer units are added to form long chains, with the elimination of some by product.

Copolymers: They are formed by the polymerisation of two or more types of monomers.

Natural polymers: They are formed in nature by plants.

Synthetic polymers: They are formed artificially by using certain chemical compounds.

Cross-linked polymers: In these polymers, monomer units are linked to give a three dimensional solid network with cross-linking.

Vulcanization: The properties of natural rubber can be modified by the process called vulcanization. On vulcanization, sulphur form cross links at reactive sites or double bonds and thus the rubber gets stiffened.

Biodegradable polymers: Polymers which disintegrate by themselves over a period of time due to environmental degradation by bacteria or other micro organism are called bio degradable polymers.

Types of detergents: There are three types of detergents, (i) Anionic detergents (ii) cationic detergenets (iii) non-ionic detergents.

Samacheer Kalvi 12th Chemistry Notes

Tamilnadu Samacheer Kalvi 12th Chemistry Notes Chapter 11 Hydroxy Compounds and Ethers Notes

Alcohols: An organic compounds containing hydroxyl (- OH) group is called alcohols.

Hydroboration:
Diborane reacts with an alkene to form trialkyl borane which on treatment with H₂O₂ in presence of NaOH gives an alcohol.

Baeyer’s reagent: Cold alkaline solution of potassium permanganate is called Baeyer’s reagent.

Saponification : The alkaline hydrolysis of these fats gives glycerol and the reaction is known as saponification.

Lucas test: When alcohols are treated with Lucas agent (a mixture of con. HC1 and anhydrous ‘ ZnCl2) they produce alkyl chloride.

Victor Meyer’s test: This test is based on the behaviour of the different nitro alkanes formed by the three types of alcohols with nitrous acid and it consists of the following steps.

• Alcohols are converted into alkyl iodide by treating it with I₂ /P.
• Alkyl iodide so formed is then treated with AgNO₂ to form nitro alkanes.
• Nitro alkanes are finally treated with HNO₂ (mixture of NaNO₂ / HCl) and the resultant solution is made alkaline with KOH.

Result:

• Primary alcohol gives red colour
• Secondary alcohol gives blue colour.
• No colouration will be observed in case of tertiary alcohol.

Elimination reactions: When alcohols are heated with a suitable dehydrating agents like sulphuric acid, the H and OH present in the adjacent carbons of alcohols are lost and it results in the formation of a carbon – carbon double bond.

Order of reactivity: The relative reactivities of alcohols in the dehydration reaction follows the order
primary < secondary < tertiary

Saytzeff’s rule: During intramolecular dehydration, if there is a possibility to form a carbon – carbon double bond at different locations, the preferred location is the one that gives the more substituted alkene (stable alkene).

Swern oxidation: In this method, dimethyl sulfoxide (DMSO) is used as the oxidising agent, which converts alcohols to ketones / aldehydes.

Biological oxidation: The fermentation of the food consumed by an animal produces alcohol. To detoxify the alcohol, the liver produces an enzyme called alcohol dehydrogenase (ADH). Nicotinamide adenine dinucleotide (NAD) present in the animals acts as a oxidising agent and ADH catalyses the oxidation of toxic alcohols into non-toxic aldehyde.

Uses of methanol:

• Methanol is used as a solvent for paints, varnishes, shellac, gums, cement, etc.
• In the manufacture of dyes, drugs, perfumes and formaldehyde.

Uses of ethanol:

• Ethanol is used as an important beverage.
• It is also used in the preparation of
• a. Paints and varnishes.
  b. Organic compounds like ether, chloroform, iodoform, etc.,
  c. Dyes, transparent soaps.
• As a substitute for petrol under the name power alcohol used as fuel for aeroplane
• It is used as a preservative for biological specimens.

Uses of ethylene glycol:

• Ethylene glycol is used as an antifreeze in automobile radiator.
• Its dinitrate is used as an explosive with DNG.

Uses of glycerol:

• Glycerol is used as a sweetening agent in confectionery and beverages.
• It is used in the manufacture of cosmetics and transparent soaps.
• It is used in making printing inks and stamp pad ink and lubricant for watches and clocks.
• It is used in the manufacture of explosive like dynamite and cordite by mixing it with chaina clay.

Phenols: They are organic compounds in which a – OH group is directly attached to a benzene ring. The carbon bearing the – OH group is sp2 hybridized.

Dows process: When Chlorobenzene is hydrolysed with 6 – 8% NaOH at 300 bar and 633K in a closed vessel,sodium phenoxide is formed which on treatment with dilute HC1 gives phenol.

Kolbe’s Schmitt reaction: In this reaction, phenol is first converted into sodium phenoxide which is more reactive than phenol towards electrophilic substitution reaction with CO₂. Treatment of sodium phenoxide with CO₂ at 400K, 4-7 bar pressure followed by acid hydrolysis gives salicylic acid.

Riemer Tiemann Reaction: On treating phenol with CHCl₃ / NaOH, a – CHO group is introduced at ortho position.

Phthalein reaction: On heating phenol with phthalic anhydride in presence of con.H₂SO₄, phenolphthalein is obtained.

Coupling reaction: Phenol couples With benzene diazonium chloride in an alkaline solution to form p-hydroxy azobenzene (a red orange dye).

Test to differentiate alcohol and phenols:

• Phenol react with benzene diazonium chloride to form a red orange dye, but ethanol has no reaction with it.
• Phenol gives purple colouration with neutral ferric chloride solution, alcohols do not give such coloration with FeCl₃.
• Phenol reacts with NaOH to give sodium phenoxide. Ethyl alcohol does not react with NaOH.

Uses of phenol:

• About half of world production of phenol is used for making phenol formaldehyde resin. (Bakelite).
• Phenol is a starting material for the preparation of
  a. drugs such as phenacetin, Salol, aspirin, etc.
  b. phenolphthalein indicator.
  c. explosive like picric acid.
• It is used as an antiseptic-carbolic lotion and carbolic soaps.

Ethers: Ethers are a class of organic compound in which an oxygen atom is connected to two alkyl / aryl groups (R – O – R’). The general formula of aliphatic ether is C_nH_2n + ₂O

Simple ethers: Both alkyl or aryl groups attached to oxygen atom are same. (R = R’)

Mixed ethers: Both alkyl or aryl groups attached to oxygen atom are different. (R ≠ R’)

Williamsons synthesis: When an alkyl halide is heated with an alcoholic solution of sodium alkoxide, the corresponding ethers are obtained. The reaction involves SN₂ mechanism.

Uses of Diethyl ether:

• Diethyl ether is used as a surgical anesthetic agent in surgery.
• It is a good solvent for organic reactions and extraction.
• It is used as a volatile starting fluid for diesel and gasoline engine.
• It is used as a refrigerant.

Uses of anisole:

• Anisole is a precursor to the synthesis of perfumes and insecticide pheromones,
• It is used as a pharmaceutical agent

pK_a Values of some alcohols and phenols:

Samacheer Kalvi 12th Chemistry Notes

Tamilnadu Samacheer Kalvi 12th Chemistry Notes Chapter 10 Surface Chemistry Notes

Surface chemistry: It is the branch of chemistry that deals with the processes occurring at interfaces between phases

Adsorbent: It is the material on which adsorption takes place.

Adsorbate: The adsorbed substacne is called adsorbate.

Interface: The surface of separation of the two phases where the concentration of adsorbed molecule is high is known as interface.

Adsorption: Adsorption is defined as the deposition of molecular species on the surface. The molecular species that get adsorbed on the surfaces is known as adsorbate and the surface on which adsorption occurs is known as adsorbent.

Absorption: It is the physical or chemical process in which atoms, molecules or ions enter some bulk phase (liquid or solid material).

Characteristics of adsorption:

• Adsorption can occur in all interfacial surfaces i.e. the adsorption can occur in between gas-solid, liquid solid, liquid-liquid, solid- solid and gas-liquid.
• Adsorption is always accompanied by decrease in free energy. When AG reaches zero, the equilibrium is attained.
• Adsorption is a spontaneous process.

Desorption: The process of removing a adsorbed substance from the surface is called desorption.

Chemical adsorption: In chemical adsorption gas molecules are held to the surface by formation of chemical bonds.

Physical adsorption: In physical adsorption, physical forces like Vanderwaals force of attraction exists between adsorbent and adsorbate.

Factors affecting adsorption: The extent fo surface adsorption depends on,

• Nature of adsorbent
• Nature of adsorbate
• Pressure
• Concentration at a given temperature

Adsorption isobars: When an amount of adsorption is plotted versus temperature at constant pressure, it is called adsorption isobar.

Adsorption isotherms: A plot between the amount of adsorbate adsorbed and pressure or concentration of adsorbate at constant temperature is called adsorption isotherms.

Catalysis: A catalyst is defined as a substance which alters the rate of chemical reaction without itself undergoing chemical change. The phenomenon which involves the action of a catalyst is called catalysis.

Positive catalysis: In positive catalysis the rate of a reaction is increased by the presence of catalyst.

Negative catalysis: In negative catalysis the rate of reaction is decreased by the presence of catalyst.

Homogeneous catalysis: In this catalysis reaction, the reactants, products and catalyst are present in the same phase.

Heterogeneous catalysis: In this catalysis reaction, the catalyst is present in a different phase (i.e.) it is not present in same phase as that of reactants or products.

Characteristics of catalysts:

• For a chemical reaction, catalyst is needed in very small quantity. Generally, a pinch of catalyst is enough for a reaction in bulk.
• There may be some physical changes, but the catalyst remains unchanged in mass and chemical composition in a chemical reaction.
• A catalyst itself cannot initiate a reaction. It means it cannot start a reaction which is not taking place. But, if the reaction is taking place in a slow rate it can increase its rate.
• A catalyst is highly effective at a particular temperature called as optimum temperature.
• Presence of a catalyst generally does not change the nature of products.

Promoters: In a catalysed reaction, the presence of a certain substance increases the activity of a
catalyst. Such a substance is called a promoter.

Catalyst poison: Certain substances when added to a catalysed reaction decreases or completely destroys the activity of catalyst and they are often known as catalytic poisons.

Auto catalysis: In certain reactions one of the products formed acts as a catalyst to the reaction.
Initially the rate of reaction will be very slow but with the increase in time the rate of reaction increases.

Active centres: The surface of a catalyst is not smooth. It bears steps, cracks and comers. Hence the atoms on such locations of the surface are co-ordinatively unsaturated. So, they have much residual force of attraction. Such sites are called active centres. So, the surface carries high surface free energy.

Enzyme Catalysis: Enzymes are complex protein molecules with three dimensional structures. They catalyse the chemical reaction in living organism. They are often present in colloidal state and extremely specific in catalytic action. Each enzyme produced in a particular living cell can catalyse a particular reaction in the cell.

Zeolite Catalysis: Zeolites are microporous, crystalline, hydrated, alumino silicates, made of silicon and aluminium tetrahedra. There are about 50 natural zeolites and 150 synthetic zeolites. As silicon is tetravalent and aluminium is trivalent, the zeolite matrix carries extra negative charge. To balance the negative charge, there are extra framework cations for example, H+ or Na+ ions.

Phase transfer catalysis: Phase transfer catalyst to facilitate transport of a reactant in one solvent to the other solvent where the second reactant is present. As the reactants are now brought together they rapidly react and form the product.

Nano catalysis: Nano materials such a metallic nano particles, metal oxides, etc., are used as catalyst in many chemical transformation, Nano catalysts carry the advantages of both homogeneous and heterogeneous catalysis.

Colloids: It is a homogeneous mixture of two substances in which one substance (smaller proportion) is dispersed in another substance (Large proportion).

Dispersed phase and Dispersed medium: In a colloidal, the substance present in larger amount is called dispersing medium and the substance present in less amount is called dispersed phase.

Preparation of Colloids: In general, colloidals are prepared by the following methods,

• Dispersion methods: In this method larger particles are broken to colloidal dimension.
• Condensation method: In this method, smaller atom or molecules are converted into larger colloidal sized particles.

Peptisation: By addition of suitable electrolytes precipitated particles can be brought into colloidal state. The process is termed as peptisation and the electrolyte added is called peptising or dispersing agent.

Tyndall effect: When light is passed through colloidal solution, it is scattered in all directions. This effect is called Tyndall effect.

Brownian movement: The colloidal sol particles are continuously bombard with the molecules of dispersion medium and hence they follow a zigzag random, continuous movement.

Helmholtz double layer: The surface of colloidal particle adsorbs one type of ion due to preferential adsorption. This layer attracts the oppositely charged ions in the medium and hence at the boundary separating the two electrical double layers are setup. This is called as Helmholtz electrical double layer.

Electrophoresis: The migration of sol particles under the influence of electric field is called Electrophoresis.

Electro osmosis: The movement of dispersion medium under the influence of electric potential is called Electro osmosis.

Emulsion: They are colloidal solution in which a liquid is dispersed in an another liquid.
Type of Emulsion: Generally there are two types of emulsions.
(i) Oil in water (O/W) (ii) Water in oil (W/O)

Deemulsification: Emulsion can be separated into two separate layers. This process is called Deemulsification.

Cortrell’s precipitator: Carbon dust in air is solidified by cortrell’s precipitator. In it, a high potential difference of about 50,000 V is used. Th e charge on carbon is neutralized and solidified. Thus the air is free from carbon particles.

Classifications of colloids based on the physical state of dispersed phase and dispersion medium:

Shape of colloidal particles:

Example of charges of sols detected by Electrophoresis are given below:

Samacheer Kalvi 12th Chemistry Notes

Tamilnadu Samacheer Kalvi 12th Chemistry Notes Chapter 9 Electro Chemistry Notes

Electro chemistry : The branch of chemistry that deals with the study of electrical energy transport and the inter conversion of electrical and chemical energy is called electro chemistry.

Ohm’s law : At a constant temperature, the current flowing through the cell (I) is directly proportional to the voltage across the cell (V)
I ∝ V
(OR)
I = V/R
(OR) V = IR

Resistivity: Resistance of an electrolytic solution is directly proportional to the length (1) and inversely proportional to the cross sectional area (A)
R ∝ l/A

Conductivity: The reciprocal of the resistance gives the conductance of an electrolytic solution.
C = 1/R

Specific conductivity: The reciprocal of the specific resistance
(OR)
The conductance of a cube of an electrolytic solution of unit dimensions are called specific conductance.
\(\kappa=\frac{1}{\rho} \cdot \frac{l}{A}\)

Molar conductivity (∧_m): It is defined as the conductance of a solution containing one mole of the electrolyte dissolved in it.
\(\Lambda_{\mathrm{m}}=\frac{\kappa \times 10^{-3}}{\mathrm{M}} \mathrm{sm}^{-1} \mathrm{~m}^{3} \mathrm{~mol}^{-1} \text {(or) } \mathrm{mho} \mathrm{m}^{3} \mathrm{~mol}^{-1} \text {. }\)

Equivalent conductance (∧): It is defined as the conductance of an electrolyte solution containing one gram equivalent of the electrolyte.
\(\Lambda=\frac{\kappa \times 10^{-3}}{N} \mathrm{sm}^{-1} \mathrm{~m}^{3}\)
(gram equivalent)^-1 (or) mhom³ (gram equivalent)^-1.

Kohlraush’s law: At infinite dilution, the limiting molar conductivity of an electrolyte is equal to the sum of the limiting of molar conductivities of its constituent ions.

Application of Kohlraush’s law: Kohlraush’s law used as,

• Calculation of molar conductance at infinite dilution of a weak electrolyte.
• Calculation of degree of dissociation of weak electrolytes.
• Calculation of solubility of a sparingly soluble salts.

Electro chemical cell: It is a device which inter converts chemical into electrical energy and vice versa.

Galvanic Cell (Voltaic cell): It is a device in which a spontaneous chemical reaction generates an electric current i.e., it converts chemical energy into electrical energy. It is commonly known as a battery.

Electrolytic cell: It is a device in which an electric current from an external source drives a non-spontaneous reaction i.e., it converts electrical energy into chemical energy.

Electromotive force: The force that pushes the electrons away from the anode and pulls them towards cathode is called the electromotive force (emf) or the cell potential.

Standard Hydrogen Electrode (SHE): It is used as the reference electrode. It has been assigned an orbitary emf of exactly zero volt. It consists of a platinum electrode in contact with 1M HC1 solution and 1 atm hydrogen gas. The hydrogen gas is bubbled through the solution at 25°C.

Electrode potential (E): Electromotive force of a cell in which the electrode on the left is a standard hydrogen electrode and the electrode on the right is the electrode in question.

Standard electrode potential (E°): The value of the standard emf of a cell in which molecular hydrogen under standard pressure is oxidised to solvated protons at the left hand electrode.

Nernst equation: It is the one which relates the cell potential and the concentration of the species involved in an electrochemical reaction.

Electrolysis: The process of chemical decomposition of an electrolyte in solution or molten state by the passage of electric current is called electrolysis.

Faraday’s first law of electrolysis: 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 ∝ Q (OR) m ∝ It (OR) m = Z It.

Faraday’s second law of electrolysis: 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.

Electrochemical equivalent: It is defined as the amount of substance deposited or liberated at the electrode by a charge of one coulomb (one ampere current passing for one second).

Battery: It is a device that produces electrons through electrochemical reactions, and contains positive and negative terminals. A battery consists of one or more electro chemical cells, which transform stored chemical energy directly into electrical energy.

Fuel cell: The galvanic cell in which the energy of combustion of fuels is directly converted into electrical energy is called the fuel cell.

Corrosion: The spontaneous destruction of metals due to their interaction with environment
is called corrosion.

Protection of metals from corrosion: Following methods helps to protect metals from corrosion,

• Coating metal surface by paint.
• Galvanizing – by coating with another metal such as zinc.
• Cathodic protection

1. Variation of molar conductivity with concentration.

2. ∧°m values for various compounds.

Samacheer Kalvi 12th Chemistry Notes

Tamilnadu Samacheer Kalvi 12th Chemistry Notes Chapter 8 Ionic Equilibrium Notes

Acid: The term ‘acid’ is derived from the latin word ‘acidus’ meaning sour, which turns the blue litmus into red.

Base: Base tastes bitter and turns the red litmus to blue.

Arrhenius Concept:

• An acid is a substance that dissociates to give hydrogen ions in water.
• A base is a substance that dissociates to give hydroxyl ions in water.

Limitations of Arrhenius Concept:

• Arrhenius theory does not explain the behaviour of acids and bases in non aqueous ‘ solvents such as acetone, Tetrahydrofuran etc.
• This theory does not account for the basicity of the substances like ammonia (NH₃) which do not possess hydroxyl group.

Lowry – Bronsted Theory :

• An acid is defined as a substance that has a tendency to donate a proton to another substance.
• A base is a substance that has a tendency to accept a proton form other substance.

Limitations of Lowry – Bronsted Theory :
Substances like BF₃, AlCl₃ etc., that do not donate protons are known to behave as acids.

Lewis concept:

• An acid is a species that accepts an electron pair (Lewis acid)
• Base is a species that donates an electron pair. (Lewis base)

Strong acid : A strong acid is the one that is almost completely dissociated in water.

Weak acid : A weak acid is only partially dissociated in water.

Auto ionisation of water : The pure water itself has a little tendency to dissociate.
i.e., one water molecule donates a proton to an another water molecule. This is known as auto ionisation of water.

pH scale : The term pH is derived from the French word ‘Purissance de hydrogene’ meaning, the power of hydrogen. It is defined as the negative logarithm of base 10 of the molar concentration of the hydronium ions present in the solution.

Ostwald’s dilution law : Ostwald’s dilution law relates the dissociation constant of the weak acid (K_a) with its degree of dissociation (α) and the concentration (c).

Degree of dissociation (α): It is the fraction of the total number of moles of a substance that dissociates at equilibrium.

Common ion effect: The dissociation of the weak acid is suppressed in the presence of a salt containing an ion common to the weak electrolyte. It is called the Common ion effect.

Buffer solution : Buffer is a solution which consists of a mixture of a weak acid and its conjugate base (or) a weak base and its conjugate acid. This buffer solution resists drastic changes in its pH upon addition of a small quantities of acids (or) bases, and this ability is called buffer action.

Types of Buffer Solution : There are two types of buffer solutions.

1. Acidic buffer solution : a solution containing a weak acid and its salt.
   Example : solution containing acetic acid and sodium, acetate
2. Basic buffer solution : a solution containing a weak base and its salt.
   Example : Solution containing NH₄OH and NH₄Cl

Buffer index : Buffer index ‘β’ is defined as the number of gram equivalents of acid or base added to one litre of the buffer solution to change its pH by unity.\(\beta=\frac{\mathrm{dB}}{\mathrm{d}(\mathrm{pH})}\)

Here,
dB = number of gram equivalents of acid / base added to one litre of buffer solution.
d(pH) = The change in the pH after the addition of acid / base.

Salt Hydrolysis : Salts completely dissociate in aqueous solutions to give their constituent ions. The ions so produced are hydrated in water. In certain cases, the cation, anion or both react with water and the reaction is called salt hydrolysis.

Solubility Product: It is defined as the product of the molar concentration of the constituent ions, each raised to the power of its stoichiometric co-efficient in a balanced equilibrium equation.

Molar solubility : The maximum number of moles of solute that can be dissolved in one litre of the solution.

Difference between Lewis acids and Lewis base:

Kw values at different temperatures are given in the following table.

Samacheer Kalvi 12th Chemistry 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