Kerala Plus Two Chemistry cheat sheet

Raoult's law for a volatile solute: p_total = p1°x1 + p2°x2. For a nonvolatile solute, p = p°x_solvent and relative lowering (p°−p)/p° = x_solute.

Colligative properties depend on the number of solute particles, not their nature: ΔTb = Kb m, ΔTf = Kf m, and π = CRT for dilute solutions.

van't Hoff factor i = observed colligative effect / calculated effect; for dissociation into n ions i = 1 + (n−1)α, and for association i = 1 − α + α/n.

Molarity = moles solute per litre of solution and is temperature-dependent; molality = moles solute per kg solvent and is temperature-independent.

Henry's law: p = K_H x. A larger K_H means lower gas solubility; gas solubility decreases with rising temperature and increases with pressure.

Ideal solutions have ΔH_mix = 0, ΔV_mix = 0, and obey Raoult's law over the whole composition range; positive deviation means weaker A–B forces, negative deviation means stronger A–B forces.

Minimum-boiling azeotropes arise from positive deviation; maximum-boiling azeotropes arise from negative deviation.

Osmosis moves solvent through a semipermeable membrane toward the more concentrated solution; isotonic solutions have equal osmotic pressure, and reverse osmosis is used for desalination.

At 298 K, the Nernst equation is E = E° − (0.0591/n) log Q, where Q is the reaction quotient and n is the number of electrons transferred.

E°cell = E°cathode − E°anode; a positive E°cell means ΔG° is negative and the cell reaction is spontaneous. At 298 K, log K = nE°cell/0.0591.

Conductance G = 1/R; conductivity κ = G l/A; molar conductivity Λm = κ/c, with c in mol m⁻³ and Λm usually in S m² mol⁻¹.

For strong electrolytes, Λm decreases linearly with √c; for weak electrolytes the plot is curved and Λ°m is obtained using Kohlrausch's law.

Kohlrausch's law: Λ°m = ν+λ°+ + ν−λ°−. For a weak electrolyte, α = Λm/Λ°m and Ka = cα²/(1−α).

Faraday's laws give mass deposited m = (ItM)/(zF), where F = 96500 C mol⁻¹ of electrons and z is the electron change per ion.

In a galvanic cell, oxidation occurs at the negative anode and reduction at the positive cathode; electrons flow through the external circuit from anode to cathode.

Lead-acid and nickel-cadmium cells are secondary batteries; Leclanché cells are primary; hydrogen-oxygen fuel cells convert chemical energy directly into electrical energy.

Iron rusting is electrochemical: iron is oxidised at the anode and oxygen is reduced at the cathode; both oxygen and water are required, and galvanising protects iron sacrificially.

Rate = −(1/a)d[A]/dt for reactant A; the rate law is determined experimentally and need not match the stoichiometric equation.

Order is the sum of concentration exponents in the rate law and can be zero, fractional, or negative; molecularity applies only to an elementary step.

Zero order: [A] = [A]0 − kt and t1/2 = [A]0/(2k); first order: ln[A] = ln[A]0 − kt and t1/2 = 0.693/k.

Second order: 1/[A] = 1/[A]0 + kt and t1/2 = 1/(k[A]0); a first-order half-life is independent of initial concentration.

Arrhenius equation: k = A e^(−Ea/RT). A plot of ln k against 1/T has slope −Ea/R, and ln(k2/k1) = (Ea/R)(1/T1 − 1/T2).

Collision theory requires sufficient collision frequency, correct orientation, and energy at least equal to Ea; the activated complex is at the transition state.

A catalyst lowers Ea and increases the rate without changing ΔH or the equilibrium constant; the slowest elementary step is the rate-determining step.

A pseudo-first-order reaction occurs when one reactant is present in large excess, for example acid-catalysed hydrolysis of an ester in water.

A transition element has an atom or common ion with an incomplete d subshell; characteristics include variable oxidation states, coloured ions, paramagnetism, catalysis, and complex formation.

Across the 3d series, atomic radii first decrease and then remain nearly constant; Cr is 3d⁵4s¹ and Cu is 3d¹⁰4s¹ because extra stability is gained by half-filled or fully filled d subshells.

Sc³⁺, Ti⁴⁺, V⁵⁺, Cr⁶⁺, and Zn²⁺ are d⁰ or d¹⁰ and colourless; Mn²⁺ is pale pink, Cu²⁺ is blue, and Fe³⁺ is yellow-brown in aqueous solution.

KMnO4 in acidic medium is reduced to Mn²⁺, in neutral medium to MnO2, and in alkaline medium to MnO4²⁻; acidified K2Cr2O7 is reduced to Cr³⁺.

Lanthanoid contraction is the steady decrease in atomic and ionic radii from La to Lu due to poor shielding by 4f electrons; it makes Y and lanthanoids similar in size and chemistry.

Ce⁴⁺ is a strong oxidising agent and Eu²⁺ is a strong reducing agent; actinoid contraction is greater than lanthanoid contraction because 5f electrons shield poorly.

Interstitial compounds form when small atoms such as C or N occupy holes in a metal lattice; they are often nonstoichiometric, hard, high melting, and retain metallic conductivity.

Brass is Cu-Zn, bronze is Cu-Sn, German silver is Cu-Zn-Ni, and an amalgam is an alloy containing mercury.

In nomenclature, ligands are named alphabetically; anionic ligands end in -o, neutral ligands include aqua and ammine, and the metal oxidation state is shown in Roman numerals.

Coordination number is the number of donor atoms bonded to the central metal; CN 2 is linear, CN 4 is tetrahedral or square planar, and CN 6 is octahedral.

Isomerism includes geometrical cis-trans and fac-mer, optical, ionization, hydrate, linkage, and coordination isomerism.

VBT examples: [Fe(CN)6]³⁻ is low-spin d²sp³ octahedral; [FeF6]³⁻ is high-spin sp³d² octahedral; [Ni(CN)4]²⁻ is dsp² square planar; [NiCl4]²⁻ is sp³ tetrahedral.

Crystal-field theory splits d orbitals by Δo; strong-field ligands give large splitting and low-spin complexes. The spectrochemical series is I⁻ < Br⁻ < Cl⁻ < F⁻ < H2O < NH3 < CN⁻ < CO.

The chelate effect is the extra stability of complexes with polydentate ligands; EDTA is hexadentate and forms stable complexes with many metal ions.

Effective atomic number = atomic number − oxidation state + 2 × coordination number; it is useful but not obeyed by all complexes.

Chlorophyll contains Mg, haemoglobin contains Fe, vitamin B12 contains Co, and cisplatin is a platinum complex used in cancer chemotherapy.

SN1 is a two-step mechanism with rate-determining carbocation formation; tertiary haloalkanes react fastest, and a chiral substrate gives racemisation.

SN2 is a one-step backside attack with inversion of configuration; the rate depends on substrate and nucleophile, and primary haloalkanes react fastest.

Haloarenes are much less reactive toward nucleophilic substitution because the C–X bond has partial double-bond character from delocalisation of the halogen lone pair into the ring.

Haloalkanes are prepared from alcohols using HX, PX3, or SOCl2; haloarenes are prepared by halogenation of benzene with X2 and FeX3.

Finkelstein reaction: RCl or RBr + NaI in dry acetone gives RI; Swarts reaction: RCl + AgF or SbF3 gives RF.

Alcoholic KOH causes dehydrohalogenation to an alkene, with Saytzeff's rule favouring the more substituted alkene; KCN gives a nitrile and NH3 gives an amine.

Haloalkanes form Grignard reagents with magnesium in dry ether; the carbon attached to Mg becomes nucleophilic.

CFCs deplete stratospheric ozone, DDT is persistent and bioaccumulates, and many organohalogens are restricted because of environmental toxicity.

Lucas test: with anhydrous ZnCl2 in concentrated HCl, tertiary alcohols turn cloudy immediately, secondary alcohols on warming, and primary alcohols do not react readily at room temperature.

Phenol is more acidic than alcohols because the phenoxide ion is resonance-stabilised; electron-withdrawing substituents increase phenol acidity and electron-donating groups decrease it.

Phenol gives a violet colour with neutral FeCl3 and a white precipitate of 2,4,6-tribromophenol with bromine water; phenol does not liberate CO2 from NaHCO3.

Williamson synthesis prepares ethers from sodium alkoxide and a primary alkyl halide by SN2; tertiary halides favour elimination instead.

With HX, the reactivity order is HI > HBr > HCl; tertiary alcohols react by SN1 and primary alcohols by SN2.

Acid-catalysed dehydration of alcohols gives alkenes, and Saytzeff's rule favours the more substituted alkene.

Oxidation gives an aldehyde from a primary alcohol, a ketone from a secondary alcohol, and no easy oxidation for a tertiary alcohol; PCC stops oxidation at the aldehyde.

Cumene process gives phenol and acetone; Reimer-Tiemann gives salicylaldehyde; Kolbe reaction gives salicylic acid.

Aldehydes are more reactive than ketones toward nucleophilic addition because the carbonyl carbon is less sterically hindered and less electron-rich.

Nucleophilic addition products include cyanohydrins with HCN, bisulfite adducts with NaHSO3, alcohols with Grignard reagents, and acetals with alcohols.

Tollens' test uses ammoniacal silver nitrate: aldehydes give a silver mirror, while most ketones do not. Fehling's solution is reduced by aliphatic aldehydes but not aromatic aldehydes.

Iodoform test: acetaldehyde, ethanol, and methyl ketones give yellow CHI3 with I2 and NaOH; other ketones do not.

Aldol condensation requires an α-hydrogen and gives a β-hydroxy carbonyl, which may dehydrate; Cannizzaro reaction occurs with aldehydes lacking α-hydrogen in concentrated base.

Carboxylic acids are more acidic than phenols and alcohols; electron-withdrawing groups increase acidity and alkyl groups decrease it.

Carboxylic acids liberate CO2 from NaHCO3 and form esters with alcohols in the presence of concentrated H2SO4.

Clemmensen reduction uses Zn-Hg/HCl, Wolff-Kishner uses NH2NH2/KOH, Rosenmund uses H2/Pd-BaSO4, and Etard uses CrO2Cl2.

In aqueous solution, basicity of methylamines is (CH3)2NH > CH3NH2 > (CH3)3N > NH3; aniline is weaker than ammonia because the nitrogen lone pair is delocalised into the ring.

Hinsberg test: a primary amine gives an alkali-soluble sulfonamide, a secondary amine gives an insoluble sulfonamide, and a tertiary amine gives no sulfonamide.

Carbylamine test: a primary amine with CHCl3 and KOH gives a foul-smelling isocyanide; secondary and tertiary amines do not respond.

Hofmann bromamide degradation converts an amide to a primary amine with one fewer carbon atom; Gabriel phthalimide synthesis gives a pure primary amine.

Diazotisation of aniline uses NaNO2 and HCl at 0–5 °C to form benzenediazonium chloride, which is unstable and useful for substitution and coupling.

Diazonium coupling with phenol is favoured at pH 8–10 and with aniline at pH 4–5; the product is an azo dye.

Sandmeyer reaction replaces the diazonium group using CuCl, CuBr, or CuCN; H3PO2 replaces it with hydrogen.

Amines react with acid chlorides to form amides; tertiary amines lack an N–H bond and cannot form such amides.

Glucose is an aldohexose and fructose is a ketohexose; sucrose is glucose + fructose and is nonreducing; lactose is glucose + galactose; maltose is glucose + glucose.

Reducing sugars have a free anomeric hydroxyl and reduce Tollens' or Fehling's reagent; glucose, fructose, maltose, and lactose are reducing, while sucrose is not.

Starch contains amylose and amylopectin; cellulose is a β-D-glucose polymer and is not digested by humans.

Amino acids contain amino and carboxyl groups and exist as zwitterions near the isoelectric point; peptide bonds link amino acids in proteins.

Protein structure has primary sequence, secondary α-helix or β-sheet, tertiary three-dimensional folding, and quaternary subunit assembly; denaturation destroys the native structure.

Enzymes are highly specific biological catalysts that lower activation energy; cofactors and coenzymes assist catalysis, and activity depends on pH and temperature.

Fat-soluble vitamins are A, D, E, and K; water-soluble vitamins include B and C. Deficiency of A causes night blindness, B1 beriberi, C scurvy, and D rickets.

DNA contains deoxyribose and bases A, T, G, C with A–T and G–C pairing; RNA contains ribose and uracil instead of thymine. Insulin is a protein hormone that lowers blood glucose.

A primary standard is highly pure, stable, non-hygroscopic, and has a high molar mass; oxalic acid and potassium hydrogen phthalate are primary standards, while NaOH and KMnO4 are not.

For a titration aA + bB, use M1V1/n1 = M2V2/n2, where n1 and n2 are the stoichiometric coefficients; at the equivalence point, equivalents of acid and base are equal.

Flame tests: Na is yellow, K violet, Ca brick red, Ba apple-green, and Cu blue-green.

Sulphate gives a white BaSO4 precipitate insoluble in dilute HCl; chloride gives white AgCl soluble in ammonia; bromide gives pale yellow AgBr; iodide gives yellow AgI.

Nitrate gives the brown ring test with iron(II) sulphate and concentrated sulphuric acid at the interface.

Phenol gives violet colour with FeCl3; aldehydes reduce Tollens' reagent; carboxylic acids liberate CO2 from NaHCO3; primary amines give the carbylamine test.

Chromatography separates by differential adsorption or partition; Rf = distance travelled by solute / distance travelled by solvent front under fixed conditions.

Concentrated acid must be added slowly to water, not water to acid, because dilution is highly exothermic; volumetric results are reported with correct units and significant figures.