CBSE · Class 12 · Chemistry

Chemistry Formula Sheet

69 formulas across 10 chapters — with variables explained and exam tips where needed.

Ch 1Solutions(9 formulas)

Molarity

mol/L

M = (moles of solute) / (volume of solution in L)

Molality

mol/kg

m = (moles of solute) / (mass of solvent in kg)

Mole fraction

χ_A = n_A / (n_A + n_B)

Mass percentage

w/w% = (mass of solute / mass of solution) × 100

Raoult's Law

p_A = χ_A × p°_A

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For ideal solutions

Elevation in boiling point

ΔT_b = K_b × m

K_b = ebullioscopic constant, m = molality

Depression in freezing point

ΔT_f = K_f × m

K_f = cryoscopic constant

Osmotic pressure

π = CRT = (n/V)RT

R = 0.0821 L·atm/mol·K

van't Hoff factor

i = observed colligative property / calculated value (assuming no association/dissociation)

Ch 2Electrochemistry(7 formulas)

Nernst Equation

E_cell = E°_cell − (0.0592/n) log Q (at 25°C)

n = moles of electrons, Q = reaction quotient

Gibbs free energy and EMF

ΔG° = −nFE°_cell

F = 96485 C/mol (Faraday constant)

Faraday's First Law

m = ZIt = (M/nF)It

Z = electrochemical equivalent, I = current, t = time

Conductance

S (Siemens)

G = 1/R = κ × A/l

Molar conductivity

S·cm²/mol

Λ_m = κ × 1000/C

C = concentration in mol/L

Kohlrausch's Law

Λ°_m = ν₊λ°₊ + ν₋λ°₋

Relation between ΔG and K

ΔG° = −RT lnK = −nFE°_cell

Ch 3Chemical Kinetics(5 formulas)

Rate of reaction

rate = −(1/a) d[A]/dt = k[A]ⁿ[B]ᵐ

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Overall order = n + m

First order rate constant

s⁻¹

k = (2.303/t) log([A]₀/[A])

Half-life (first order)

t₁/₂ = 0.693/k

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Independent of initial concentration

Arrhenius Equation

k = Ae^(−Ea/RT)

Ea = activation energy, A = frequency factor, R = 8.314 J/mol·K

Arrhenius (log form)

log(k₂/k₁) = (Ea/2.303R)(1/T₁ − 1/T₂)

Ch 4d and f Block Elements(6 formulas)

Spin-only magnetic moment

μ = √[n(n+2)] BM

n = number of unpaired electrons, BM = Bohr Magneton

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Appears every year — memorise the √[n(n+2)] formula

Lanthanide contraction

Atomic/ionic radius decreases from La to Lu due to poor shielding by 4f electrons

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Consequence: similar atomic radii of 4d and 5d transition metals

Oxidation state of Mn in KMnO₄

K: +1, O: −2 → Mn = +7

Oxidation state of Cr in K₂Cr₂O₇

2K: +1, 7O: −2 → 2Cr = +12 → Cr = +6

MnO₄⁻ in acidic medium (oxidation)

MnO₄⁻ + 8H⁺ + 5e⁻ → Mn²⁺ + 4H₂O

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Reduction half-reaction; used in titrations

Cr₂O₇²⁻ in acidic medium (oxidation)

Cr₂O₇²⁻ + 14H⁺ + 6e⁻ → 2Cr³⁺ + 7H₂O

Ch 5Coordination Compounds(5 formulas)

Oxidation state of central metal

Charge on complex = charge on metal + sum of charges of all ligands

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For neutral complex: metal charge = −(sum of ligand charges)

EAN (Effective Atomic Number)

EAN = atomic number − oxidation state + 2 × coordination number

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Secondary valence = coordination number

Crystal Field Splitting (octahedral)

Δₒ = energy of eₘ − energy of t₂g

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Strong field ligands give large Δₒ (low spin); weak field give small Δₒ (high spin)

Spectrochemical series (abridged)

I⁻ < Br⁻ < Cl⁻ < F⁻ < OH⁻ < H₂O < NH₃ < en < CN⁻ < CO (weak → strong field)

IUPAC naming rule

Anionic ligands end in -o; neutral: aqua, ammine, carbonyl; cationic: no change. Ligands named alphabetically before metal.

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Metal in brackets; counter ion outside

Ch 6Haloalkanes and Haloarenes(5 formulas)

Rate of SN2

rate = k[RX][Nu⁻]

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Bimolecular: inversion of configuration (Walden inversion). Order: CH₃X > 1° > 2° > 3°

Rate of SN1

rate = k[RX]

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Unimolecular: racemisation. Order: 3° > 2° > 1° > CH₃X. Carbocation intermediate.

Optical rotation

R configuration: clockwise (+d); S configuration: anticlockwise (−l). Racemic mixture: zero rotation.

Reactivity order (nucleophilic substitution)

RI > RBr > RCl > RF

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C−I bond weakest (largest halogen), so most reactive

Bond polarity (C−X)

C−F most polar (highest electronegativity of F); C−I least polar but most reactive (weakest bond)

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Polarity ≠ reactivity in haloalkanes

Ch 7Alcohols, Phenols and Ethers(7 formulas)

Lucas test reagent

Conc. HCl + anhydrous ZnCl₂

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3° alcohol: immediate turbidity; 2°: turbid in 5 min; 1°: no turbidity at room temperature

Acidity of phenol

PhOH → PhO⁻ + H⁺ (pKa ≈ 10)

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More acidic than alcohols (pKa ~16) due to resonance stabilisation of phenoxide ion

Williamson synthesis

R−O⁻Na⁺ + R′X → R−O−R′ + NaX

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Best for unsymmetrical ethers; alkyl halide must be primary to avoid elimination

Dehydration of alcohol (intramolecular)

R−CH₂−CH₂−OH →(conc. H₂SO₄, 170°C)→ alkene + H₂O

Dehydration of alcohol (intermolecular)

2 R−OH →(conc. H₂SO₄, 140°C)→ R−O−R + H₂O

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Lower temp gives ether; higher temp gives alkene

Kolbe-Schmitt reaction

PhONa + CO₂ →(high pressure, 125°C)→ Sodium salicylate →(H⁺)→ Salicylic acid

Reimer-Tiemann reaction

Phenol + CHCl₃ + NaOH → 2-hydroxybenzaldehyde (ortho) major product

Ch 8Aldehydes, Ketones and Carboxylic Acids(11 formulas)

Tollens' test (silver mirror)

RCHO + 2[Ag(NH₃)₂]⁺ + 2OH⁻ → RCOO⁻ + 2Ag↓ + 4NH₃ + H₂O

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Positive for aldehydes only; ketones give no reaction

Fehling's test

RCHO + 2Cu²⁺ (Fehling's) + 5OH⁻ → RCOO⁻ + Cu₂O↓(red) + 3H₂O

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Positive for aliphatic aldehydes; aromatic aldehydes and ketones give no reaction

Aldol condensation

2 CH₃CHO →(dil. NaOH)→ CH₃CH(OH)CH₂CHO (3-hydroxybutanal)

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Requires α-hydrogen; product: β-hydroxy carbonyl compound → α,β-unsaturated carbonyl on heating

Cannizzaro reaction

2 HCHO →(conc. NaOH)→ CH₃OH + HCOONa

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For aldehydes with no α-hydrogen (HCHO, PhCHO); disproportionation

Clemmensen reduction

R−CO−R′ + Zn(Hg)/conc. HCl → R−CH₂−R′

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Reduces carbonyl to methylene (−CH₂−); acidic medium; for acid-sensitive compounds use Wolff-Kishner

Wolff-Kishner reduction

R−CO−R′ + NH₂NH₂ → (KOH, ethylene glycol, Δ) → R−CH₂−R′ + N₂

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Reduces carbonyl to methylene in basic medium

Rosenmund reduction

RCOCl + H₂ →(Pd/BaSO₄)→ RCHO + HCl

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Converts acid chloride to aldehyde; Pd poisoned with BaSO₄ to prevent over-reduction

Etard reaction

C₆H₅CH₃ + CrO₂Cl₂ →(CS₂)→ [complex] →(H₂O)→ C₆H₅CHO

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Oxidises −CH₃ on benzene ring selectively to −CHO

Gattermann-Koch reaction

C₆H₆ + CO + HCl →(AlCl₃/CuCl)→ C₆H₅CHO

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Converts benzene directly to benzaldehyde using CO + HCl as formylating agent

HVZ reaction

RCH₂COOH + X₂ →(P)→ RCH(X)COOH + HX

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Halogenation at α-carbon of carboxylic acid using PCl₃ or P

Esterification

RCOOH + R′OH ⇌ (H⁺, Δ) RCOOR′ + H₂O

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Reversible; equilibrium shifted right by excess alcohol or removal of water

Ch 9Amines(9 formulas)

Basicity order of amines (aliphatic)

R₂NH > RNH₂ > R₃N > NH₃ (in aqueous solution)

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3° amine less basic than 2° in water due to solvation effect

Basicity: aliphatic vs aromatic

Aliphatic amines (pKa ~10) >> Aromatic amines (pKa ~4.6 for aniline)

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Lone pair on N delocalised into ring in aniline → less available for protonation

Hinsberg test

1° amine + C₆H₅SO₂Cl → N-alkylbenzenesulfonamide (soluble in NaOH); 2° amine → N,N-dialkyl product (insoluble in NaOH); 3° amine → no reaction

Gabriel synthesis

Phthalimide −(KOH)→ K-phthalimide −(RX)→ N-alkylphthalimide −(H₂NNH₂ or H₃O⁺)→ RNH₂

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Gives only primary amines; cannot prepare 2° or 3°

Hofmann bromamide degradation

RCONH₂ + Br₂ + 4NaOH → RNH₂ + Na₂CO₃ + 2NaBr + 2H₂O

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One carbon is lost; amide → primary amine with one fewer C

Diazotisation

ArNH₂ + NaNO₂ + 2HCl →(0–5°C)→ ArN₂⁺Cl⁻ + NaCl + 2H₂O

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Must keep temperature 0–5°C; diazonium salt decomposes above 5°C

Sandmeyer reaction

ArN₂⁺Cl⁻ + CuX →(Cu)→ ArX + N₂ (X = Cl, Br, CN)

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Replaces −NH₂ with −Cl, −Br, or −CN via diazonium salt

Balz-Schiemann reaction

ArN₂⁺Cl⁻ + HBF₄ → ArN₂⁺BF₄⁻ →(Δ)→ ArF + N₂ + BF₃

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Only reliable way to introduce −F into aromatic ring

Coupling reaction

ArN₂⁺ + PhOH (alkaline) → Ar−N=N−Ph(OH) (azo dye, orange/red)

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Electrophilic aromatic substitution; diazonium ion attacks phenol/amine

Ch 10Biomolecules(5 formulas)

Chargaff's Rule

A = T | G = C | A + G = T + C (purines = pyrimidines)

DNA base percentage from A%

T% = A% | G% = C% = (100 − 2A%) / 2

H-bonds in DNA

Total H-bonds = 2×(A=T pairs) + 3×(G≡C pairs)

Number of peptide bonds

Peptide bonds = n − 1 (n = number of amino acids in chain)

Reducing vs non-reducing sugars

Reducing: free aldehyde or ketone group (glucose, fructose, maltose, lactose). Non-reducing: no free group (sucrose, cellulose, starch).

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Sucrose is non-reducing; positive Fehling's/Tollens' means reducing sugar

More for CBSE Class 12

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Chemistry Formula Sheet — Class 12