Revision notesClass 11 and 12
Chemistry Quick Revision for JEE and NEET
Physical chemistry formulas, inorganic trends and the organic reactions examiners return to most often, condensed onto a few pages for the last weeks before JEE or NEET.
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01Mole concept and solutions
- Moles n = mass/molar mass = number of particles/NA
- Molarity M = moles of solute/litres of solution; molality m = moles of solute/kg of solvent
- Mole fraction xA = nA/(nA + nB)
- Normality N = M × n-factor; dilution M1V1 = M2V2
- Raoult's law pA = xAp°A; relative lowering (p° − p)/p° = xsolute
- Colligative properties ΔTb = iKbm; ΔTf = iKfm; osmotic pressure π = iCRT
- Henry's law p = KHx
02Atomic structure
- Bohr energy En = −13.6 Z2/n2 eV; radius rn = 0.529 n2/Z Å
- de Broglie λ = h/mv; Heisenberg Δx·Δp ≥ h/4π
- Quantum numbers n; l from 0 to n − 1; ml from −l to +l; ms = ±½
- Capacity 2n2 electrons per shell; 2l + 1 orbitals per subshell
- Nodes radial n − l − 1; angular l
- Filling order (n + l) rule, then Pauli exclusion and Hund's rule
03Gases
- Ideal gas PV = nRT, R = 0.0821 L atm mol−1 K−1 = 8.314 J mol−1 K−1
- Dalton pi = xiptotal
- Graham rate ∝ 1/√M
- van der Waals (P + an2/V2)(V − nb) = nRT
- Compressibility Z = PV/nRT
- Molecular speeds urms = √(3RT/M), uavg = √(8RT/πM), ump = √(2RT/M)
04Thermodynamics
- First law ΔU = q + w (w = work done on the system); w = −PextΔV
- Enthalpy ΔH = ΔU + ΔngRT; Hess's law adds reaction enthalpies
- Gibbs energy ΔG = ΔH − TΔS; spontaneous when ΔG < 0
- Link to equilibrium ΔG° = −RT ln K = −2.303RT log K
- Link to cells ΔG° = −nFE°cell
05Equilibrium
- Kp and Kc Kp = Kc(RT)Δn
- pH pH = −log[H+]; pH + pOH = 14 and Kw = 10−14 at 25 °C
- Weak acid [H+] = √(KaC), degree of dissociation α = √(Ka/C)
- Buffer (Henderson) pH = pKa + log([salt]/[acid])
- Salt of weak acid and strong base pH = 7 + ½(pKa + log C)
- Solubility product Ksp = s2 for AB; 4s3 for AB2
06Electrochemistry and kinetics
- Cell emf E°cell = E°cathode − E°anode
- Nernst equation (298 K) E = E° − (0.0591/n) log Q
- Faraday's law m = (M/nF)It, F = 96,500 C mol−1
- Conductivity Λm = κ × 1000/M (κ in S cm−1); Kohlrausch Λ°m = ν+λ°+ + ν−λ°−
- Zero order t½ = [A]0/2k
- First order k = (2.303/t) log([A]0/[A]), t½ = 0.693/k
- Arrhenius k = Ae−Ea/RT; log(k2/k1) = [Ea/2.303R](1/T1 − 1/T2)
07Periodic trends and bonding
- Atomic radius decreases across a period, increases down a group
- Ionisation enthalpy increases across a period; exceptions N > O, Be > B, Mg > Al
- Electronegativity fluorine is highest (4.0 on the Pauling scale); chlorine has the most negative electron gain enthalpy
- Bond order (MOT) (Nb − Na)/2; O2 has bond order 2 and is paramagnetic; N2 has bond order 3
- Hybridisation 2 sp linear; 3 sp2 trigonal planar; 4 sp3 tetrahedral; 5 sp3d trigonal bipyramidal; 6 sp3d2 octahedral
- Shapes H2O bent 104.5°; NH3 pyramidal 107°; SF4 see-saw; ClF3 T-shaped; XeF2 linear; XeF4 square planar
- Formal charge valence electrons − non-bonding electrons − ½ bonding electrons
08Coordination compounds
- Crystal field (octahedral) t2g −0.4Δo, eg +0.6Δo
- Spectrochemical series I− < Br− < Cl− < F− < OH− < H2O < NH3 < en < CN− < CO
- Magnetic moment (spin only) μ = √[n(n + 2)] BM, n = unpaired electrons
09Named reactions
- Aldol aldehydes or ketones with α-H in dilute alkali give β-hydroxy carbonyl compounds
- Cannizzaro aldehydes without α-H in concentrated alkali give an alcohol and a carboxylate
- Wurtz 2R–X + 2Na in dry ether give R–R
- Friedel–Crafts alkylation or acylation of benzene with AlCl3
- Reimer–Tiemann phenol + CHCl3 + NaOH give salicylaldehyde
- Kolbe sodium phenoxide + CO2 give salicylic acid
- Hell–Volhard–Zelinsky carboxylic acid + X2/red P gives the α-halo acid
- Hoffmann bromamide amide + Br2/NaOH gives an amine with one carbon fewer
- Sandmeyer diazonium salt + CuX gives an aryl halide
- Gabriel phthalimide a route to pure primary amines
- Clemmensen and Wolff–Kishner reduce C=O to CH2 (Zn-Hg/HCl; NH2NH2/KOH)
- Rosenmund acid chloride + H2/Pd-BaSO4 gives an aldehyde
- Etard toluene + CrO2Cl2 gives benzaldehyde
- Williamson RO−Na+ + R'X gives the ether R–O–R'
10Organic rules of thumb
- Markovnikov H adds to the carbon with more hydrogens; HBr with peroxide adds anti-Markovnikov
- Substitution SN1 favours 3° > 2° > 1° and racemises; SN2 favours 1° > 2° > 3° with inversion
- Carbocation stability 3° > 2° > 1° > methyl
- Acidity carboxylic acids > phenols > water > alcohols; electron-withdrawing groups raise acidity
11Laboratory tests
- Tollens' reagent silver mirror with aldehydes
- Fehling's solution red precipitate with aliphatic aldehydes
- Iodoform test CH3CO– or CH3CH(OH)– groups give yellow CHI3
- Lucas test tertiary alcohols turn cloudy at once
- Carbylamine test primary amines give a foul-smelling isocyanide
- Neutral FeCl3 violet colour with phenols
- 2,4-DNP orange precipitate with aldehydes and ketones
- Hinsberg's reagent tells primary, secondary and tertiary amines apart
How to use these notes
- Learn named reactions as reagent → product pairs, then test yourself by covering one side.
- For trends, remember the exceptions: they are what the questions ask about.
- NCERT lines are the source for most inorganic questions; read the relevant chapter after this sheet.
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