Physical Chemistry Formulas for JEE Main 2026

Physical Chemistry is the most formula-intensive part of JEE Main Chemistry, and the formulas are remarkably compact — one A4 sheet can hold every equation you need. This guide organises all Physical Chemistry formulas by chapter with the conditions under which each applies. Use this as your quick-revision reference in the final weeks before the exam.

Atomic Structure

Bohr energy: E_n = −13.6Z²/n² eV. Radius: r_n = 0.529n²/Z Å. Wavelength: 1/λ = RZ²(1/n₁² − 1/n₂²), R = 1.097 × 10⁷ m⁻¹. de Broglie: λ = h/mv = h/√(2mK). Heisenberg: Δx·Δp ≥ h/(4π). Photoelectric: KE_max = hν − φ = hν − hν₀. de Broglie for electron accelerated through V volts: λ = √(150/V) Å. For detailed treatment, see our Atomic Structure Guide.

Thermodynamics and Thermochemistry

ΔG = ΔH − TΔS. ΔG° = −RT ln K = −2.303RT log K. ΔG° = −nFE°. ΔH_reaction = Σ(bond enthalpies broken) − Σ(bond enthalpies formed) [gas phase only]. Hess's law: ΔH is path-independent. ΔH = ΔU + Δn_gas RT (Kirchhoff conversion). Heat capacity at constant pressure C_p = C_v + R (per mole ideal gas). For ideal gas: γ = C_p/C_v. Adiabatic: TV^(γ−1) = constant; TP^(−γ/(γ−1)) = constant; PV^γ = constant. Work by gas: isothermal W = nRT·ln(V₂/V₁); adiabatic W = −ΔU = nC_v(T₁−T₂).

Chemical Equilibrium

K_c = [products]^stoich / [reactants]^stoich (molarity; solids/liquids excluded). K_p = K_c(RT)^(Δn_g). van't Hoff: d(ln K)/dT = ΔH°/(RT²) → ln(K₂/K₁) = (ΔH°/R)(1/T₁ − 1/T₂). Degree of dissociation α and K_c: for A ⇌ B + C at initial concentration C: K_c = Cα²/(1−α) ≈ Cα² (if α << 1). Take a free mock test that tests Physical Chemistry formulas across all chapters.

Ionic Equilibrium

pH = −log[H⁺]. K_w = [H⁺][OH⁻] = 10⁻¹⁴ at 25°C. Weak acid: [H⁺] = √(K_a·C); pH = ½(pK_a − log C). Henderson-Hasselbalch: pH = pK_a + log([A⁻]/[HA]). Buffer capacity maximum at pH = pK_a. Salt of weak acid/strong base: pH = 7 + ½pK_a + ½log C. Salt of weak base/strong acid: pH = 7 − ½pK_b − ½log C. Ksp: for AB type s = √Ksp; for AB₂ type Ksp = 4s³. Degree of hydrolysis: h = √(K_w/(K_a·C)).

Electrochemistry

E°_cell = E°_cathode − E°_anode. ΔG° = −nFE°_cell. Nernst: E = E° − (0.0592/n)·log Q at 25°C. log K = nE°/0.0592. Faraday's law: m = (M/n)·(It/F), F = 96500 C/mol. Conductance G = 1/R; κ = G·l/A; Λ_m = 1000κ/C (C in mol/L). Kohlrausch: Λ°_m = ν₊λ°₊ + ν₋λ°₋.

Chemical Kinetics

Rate = k[A]^m[B]^n. Zero order: [A] = [A]₀ − kt; t₁/₂ = [A]₀/(2k). First order: [A] = [A]₀e^(−kt); t₁/₂ = 0.693/k (independent of concentration). Second order: 1/[A] = 1/[A]₀ + kt; t₁/₂ = 1/(k[A]₀). Arrhenius: k = Ae^(−Ea/RT); ln(k₂/k₁) = (Ea/R)(1/T₁ − 1/T₂). For integrated rate law derivations and detailed kinetics, see our Chemical Kinetics Guide.

Solutions and Colligative Properties

Raoult's law: P = x_solvent·P°. Relative lowering: (P°−P)/P° = x_solute. Boiling point elevation: ΔT_b = i·K_b·m, K_b(water) = 0.52. Freezing point depression: ΔT_f = i·K_f·m, K_f(water) = 1.86. Osmotic pressure: π = iCRT. van't Hoff factor: i = 1+(n−1)α for dissociation. Henry's law: p = K_H·x (gas solubility). For complete solutions theory, see our Solutions Guide.

Solid State and Nuclear Chemistry

packing fraction: SC 52%, BCC 68%, FCC/HCP 74%. Bragg's law: 2d·sinθ = nλ. Radioactive decay: N = N₀e^(−λt); t₁/₂ = 0.693/λ. Activity A = λN. Q-value of nuclear reaction: Q = (mass of reactants − mass of products)c².

Exam Use

Print or write this formula list on a single card and review it daily in the final month. Each formula should be recognised within one second — if it takes longer, that chapter needs another revision pass. Pair these formulas with worked examples from our 30-Day Chemistry Plan. Upgrade for ₹149/month for chapter-level tests keyed to each formula section.