Class 12 Chemistry: Solutions

• Chemistry in Class 12 covers a range of topics essential for understanding the composition, structure, properties, and reactions of matter.
• Key areas include solutions, electrochemistry, chemical kinetics, surface chemistry, coordination compounds, haloalkanes and haloarenes, alcohols, phenols, and ethers, aldehydes, ketones, and carboxylic acids, amines, biomolecules, polymers, and chemistry in everyday life.

Solutions

• Solutions are homogeneous mixtures of two or more substances.
• Solvent is the component present in the largest quantity.
• Solute is the component present in lesser quantity.
• Molarity (M) is defined as moles of solute per liter of solution.
• Molality (m) is defined as moles of solute per kilogram of solvent.
• Normality (N) is defined as gram equivalents of solute per liter of solution.
• Mole fraction (x) is the ratio of the number of moles of a component to the total number of moles in the solution.
• Henry's Law states that the solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid.
• Raoult's Law states that for a solution of volatile liquids, the partial vapor pressure of each component is directly proportional to its mole fraction in the solution.
• Ideal solutions obey Raoult's Law over the entire range of concentration.
• Non-ideal solutions do not obey Raoult's Law.
• Positive deviations from Raoult's Law occur when the vapor pressure is higher than predicted.
• Negative deviations from Raoult's Law occur when the vapor pressure is lower than predicted.
• Azeotropes are binary mixtures having the same composition in the liquid and vapor phase and boil at a constant temperature.
• Colligative properties depend on the number of solute particles, not their identity.
• Relative lowering of vapor pressure is proportional to the mole fraction of the solute.
• Elevation of boiling point is proportional to the molality of the solute.
• Depression of freezing point is proportional to the molality of the solute.
• Osmotic pressure is proportional to the molarity of the solution.
• Van't Hoff factor (i) is used to account for the dissociation or association of solute particles in solution.
• i = (Observed colligative property)/(Calculated colligative property assuming no association or dissociation)

Electrochemistry

• Electrochemical cells convert chemical energy into electrical energy and vice versa.
• Electrolytic cells use electrical energy to drive non-spontaneous chemical reactions.
• Galvanic cells (voltaic cells) produce electrical energy from spontaneous chemical reactions.
• Electrode potential is the potential difference between an electrode and the electrolyte.
• Standard electrode potential (E°) is measured under standard conditions (298 K, 1 atm pressure, 1 M concentration).
• Nernst equation relates electrode potential to the concentrations of ions.
• ΔG° = -nFE°, where ΔG° is the standard Gibbs free energy change, n is the number of moles of electrons transferred, and F is Faraday's constant (96487 C/mol).
• Conductance (G) is the reciprocal of resistance (R).
• Conductivity (κ) is the conductance of a solution of 1 cm length and area of cross-section 1 cm².
• Molar conductivity (Λm) is the conductivity of a solution containing 1 mole of electrolyte.
• Kohlrausch's Law states that the limiting molar conductivity of an electrolyte is the sum of the individual contributions of the cation and anion.
• Electrolysis is the decomposition of an electrolyte by passing electricity through its solution or molten state.
• Faraday's Laws of Electrolysis relate the amount of substance liberated at an electrode to the quantity of electricity passed.
• Batteries are galvanic cells used as a source of electrical energy.
• Primary batteries are non-rechargeable (e.g., dry cell, mercury cell).
• Secondary batteries are rechargeable (e.g., lead-acid battery, nickel-cadmium battery).
• Fuel cells convert the energy from the combustion of fuels (e.g., hydrogen) directly into electrical energy.
• Corrosion is the process by which metals are slowly eaten away by the action of air, moisture, or chemicals.

Chemical Kinetics

• Chemical kinetics is the study of reaction rates and factors affecting them.
• Rate of reaction is the change in concentration of a reactant or product per unit time.
• Average rate is measured over a long time interval.
• Instantaneous rate is the rate at a specific instant.
• Rate law expresses the rate of reaction in terms of the concentrations of reactants.
• Rate constant (k) is the proportionality constant in the rate law.
• Order of reaction is the sum of the powers of the concentration terms in the rate law.
• Molecularity is the number of reacting species involved in an elementary reaction.
• Elementary reactions are single-step reactions.
• Complex reactions consist of several elementary steps.
• Rate-determining step is the slowest step in a complex reaction.
• Integrated rate laws relate the concentration of reactants to time.
• Zero-order reactions have a constant rate.
• First-order reactions have a rate proportional to the concentration of one reactant.
• Half-life (t1/2) is the time required for the concentration of a reactant to decrease to half its initial value.
• Arrhenius equation relates the rate constant to temperature.
• k = A e-Ea/RT, where A is the pre-exponential factor, Ea is the activation energy, R is the gas constant, and T is the absolute temperature.
• Activation energy is the minimum energy required for a reaction to occur.
• Catalysts increase the rate of a reaction by lowering the activation energy.
• Homogeneous catalysts are in the same phase as the reactants.
• Heterogeneous catalysts are in a different phase from the reactants.

Surface Chemistry

• Surface chemistry deals with phenomena occurring at the surfaces or interfaces.
• Adsorption is the accumulation of molecules at the surface rather than in the bulk of a solid or liquid.
• Adsorbate is the substance being adsorbed.
• Adsorbent is the substance on whose surface adsorption occurs.
• Physisorption is physical adsorption involving weak van der Waals forces.
• Chemisorption is chemical adsorption involving chemical bond formation.
• Factors affecting adsorption include surface area, temperature, and pressure.
• Freundlich adsorption isotherm relates the amount of gas adsorbed to pressure at a constant temperature.
• Catalysis is the process of increasing the rate of a reaction using a catalyst.
• Homogeneous catalysis involves catalysts in the same phase as the reactants.
• Heterogeneous catalysis involves catalysts in a different phase from the reactants.
• Enzymes are biological catalysts.
• Colloids are heterogeneous systems in which one substance is dispersed as very fine particles in another substance.
• Dispersed phase is the substance that is scattered as particles.
• Dispersion medium is the substance in which the particles are dispersed.
• Lyophilic colloids are solvent-loving and form stable sols.
• Lyophobic colloids are solvent-hating and are easily precipitated.
• Emulsions are colloids in which both the dispersed phase and dispersion medium are liquids.
• Gels are colloids in which the liquid is dispersed in a solid.
• Micelles are aggregates of surfactant molecules in a colloidal solution.
• CMC (Critical Micelle Concentration) is the concentration above which micelles form.
• Cloud point is the temperature above which a surfactant solution becomes cloudy.

Coordination Compounds

• Coordination compounds are compounds containing a central metal atom or ion surrounded by ligands.
• Coordination entity is a central metal atom or ion bonded to a fixed number of ions or molecules.
• Central metal atom/ion is the atom/ion to which a fixed number of ions/molecules are bound in a definite geometrical arrangement around it.
• Ligands are ions or molecules bound to the central metal atom/ion.
• Coordination number is the number of ligand atoms directly attached to the central metal atom/ion.
• Coordination sphere is the central metal atom/ion and the ligands attached to it.
• IUPAC nomenclature rules provide a systematic way to name coordination compounds.
• Werner's theory explains the bonding in coordination compounds.
• Valence Bond Theory (VBT) explains the bonding and geometry of coordination compounds based on hybridization.
• Crystal Field Theory (CFT) explains the bonding and properties of coordination compounds based on the interaction between the metal ion and the ligands.
• Spectrochemical series arranges ligands in order of their ability to split d-orbitals.
• Isomerism in coordination compounds includes structural and stereoisomerism.
• Linkage isomerism arises when a ligand can coordinate through different atoms.
• Coordination isomerism arises when ligands exchange between cationic and anionic coordination entities.
• Ionization isomerism arises when the counter ion in a complex exchanges with a ligand inside the coordination sphere.
• Hydrate isomerism arises when water molecules are inside or outside the coordination sphere.
• Geometrical isomerism (cis-trans) arises in square planar and octahedral complexes.
• Optical isomerism arises when complexes are non-superimposable mirror images.
• Coordination compounds have applications in qualitative analysis, quantitative analysis, biological systems, and medicine.

Haloalkanes and Haloarenes

• Haloalkanes are alkyl halides where one or more hydrogen atoms in an alkane are replaced by halogen atoms.
• Haloarenes are aryl halides where one or more hydrogen atoms in an arene are replaced by halogen atoms.
• Nomenclature of haloalkanes and haloarenes follows IUPAC rules.
• Haloalkanes undergo nucleophilic substitution reactions (SN1 and SN2).
• SN1 reactions are unimolecular and proceed through a carbocation intermediate.
• SN2 reactions are bimolecular and proceed through a transition state with inversion of configuration.
• Haloarenes are less reactive towards nucleophilic substitution due to resonance stabilization.
• Reactions of haloalkanes include substitution, elimination, and reaction with metals.
• Reactions of haloarenes include electrophilic substitution and reactions with metals.
• Polyhalogen compounds include dichloromethane, chloroform, iodoform, carbon tetrachloride, freons, and DDT.

Alcohols, Phenols, and Ethers

• Alcohols contain one or more hydroxyl (-OH) groups attached to an alkyl group.
• Phenols contain one or more hydroxyl (-OH) groups attached to an aryl group.
• Ethers contain an oxygen atom bonded to two alkyl or aryl groups.
• Nomenclature of alcohols, phenols, and ethers follows IUPAC rules.
• Alcohols can be prepared by hydration of alkenes, hydroboration-oxidation, and reduction of carbonyl compounds.
• Phenols can be prepared from haloarenes, benzenesulfonic acid, and diazonium salts.
• Ethers can be prepared by Williamson ether synthesis and dehydration of alcohols.
• Reactions of alcohols include dehydration, oxidation, esterification, and reaction with hydrogen halides.
• Acidity of alcohols decreases with increasing alkyl substitution.
• Phenols are more acidic than alcohols due to resonance stabilization of the phenoxide ion.
• Reactions of phenols include electrophilic substitution (halogenation, nitration, sulfonation) and Kolbe's reaction.
• Reactions of ethers include cleavage by hydrogen halides.

Aldehydes, Ketones, and Carboxylic Acids

• Aldehydes contain a carbonyl group (C=O) bonded to one alkyl or aryl group and one hydrogen atom.
• Ketones contain a carbonyl group (C=O) bonded to two alkyl or aryl groups.
• Carboxylic acids contain a carboxyl group (-COOH).
• Nomenclature of aldehydes, ketones, and carboxylic acids follows IUPAC rules.
• Aldehydes and ketones can be prepared by oxidation of alcohols, ozonolysis of alkenes, and Friedel-Crafts acylation.
• Carboxylic acids can be prepared by oxidation of alcohols and aldehydes, hydrolysis of nitriles, and Grignard reagent reactions.
• Reactions of aldehydes and ketones include nucleophilic addition, reduction, oxidation, and reactions with Grignard reagents.
• Reactions of carboxylic acids include esterification, reduction, decarboxylation, and reactions with ammonia.
• Acidity of carboxylic acids is due to resonance stabilization of the carboxylate ion.

Amines

• Amines are derivatives of ammonia where one or more hydrogen atoms are replaced by alkyl or aryl groups.
• Nomenclature of amines follows IUPAC rules.
• Amines can be prepared by reduction of nitro compounds, ammonolysis of alkyl halides, reduction of nitriles, and Gabriel phthalimide synthesis.
• Basicity of amines is due to the lone pair of electrons on the nitrogen atom.
• Aliphatic amines are generally more basic than ammonia.
• Aromatic amines are less basic than ammonia due to resonance delocalization of the lone pair.
• Reactions of amines include alkylation, acylation, reaction with nitrous acid, and carbylamine reaction.
• Diazonium salts are formed by the reaction of aromatic amines with nitrous acid.

Biomolecules

• Biomolecules are organic compounds essential for life.
• Carbohydrates are polyhydroxy aldehydes or ketones.
• Monosaccharides are simple sugars (e.g., glucose, fructose).
• Disaccharides consist of two monosaccharides linked together (e.g., sucrose, lactose).
• Polysaccharides are polymers of monosaccharides (e.g., starch, cellulose).
• Proteins are polymers of amino acids.
• Amino acids contain an amino group (-NH2) and a carboxyl group (-COOH).
• Peptide bond is the amide linkage between amino acids.
• Primary structure of proteins is the sequence of amino acids.
• Secondary structure of proteins includes alpha-helix and beta-pleated sheet.
• Tertiary structure of proteins is the overall three-dimensional shape.
• Quaternary structure of proteins is the arrangement of multiple polypeptide chains.
• Enzymes are biological catalysts.
• Vitamins are organic compounds required in small amounts for various biological functions.
• Nucleic acids are polymers of nucleotides.
• DNA (deoxyribonucleic acid) contains the genetic information.
• RNA (ribonucleic acid) plays a role in protein synthesis.

Polymers

• Polymers are large molecules consisting of repeating structural units called monomers.
• Addition polymers are formed by the direct addition of monomers.
• Condensation polymers are formed with the elimination of small molecules like water or alcohol.
• Natural polymers include starch, cellulose, proteins, and natural rubber.
• Synthetic polymers include polyethylene, PVC, Teflon, nylon, and polyester.
• Thermoplastics soften on heating and can be remolded.
• Thermosetting plastics undergo irreversible changes on heating and cannot be remolded.
• Elastomers are polymers that can be stretched to several times their original length and return to their original shape.
• Biodegradable polymers can be broken down by microorganisms.

Chemistry in Everyday Life

• Drugs are chemicals used for the treatment, prevention, or diagnosis of diseases.
• Analgesics relieve pain.
• Antipyretics reduce fever.
• Antiseptics kill or prevent the growth of microorganisms on living tissues.
• Disinfectants kill microorganisms on inanimate objects.
• Tranquilizers reduce anxiety and tension.
• Antibiotics kill or inhibit the growth of bacteria.
• Antacids neutralize excess stomach acid.
• Antihistamines counteract the effects of histamine.
• Soaps and detergents are surface-active agents used for cleaning.
• Food preservatives prevent spoilage of food.
• Artificial sweetening agents provide sweetness without adding calories.