All Class 12 Chemistry formulas

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The formulas from 3 chapters, in one place to revise from or print. Open a chapter's own sheet to see where students usually slip up.

1. Solutions

Henry's law: $\displaystyle p = K_Hx$
Raoult's law: $\displaystyle p_A = p_A^\circ x_A$
Total vapour pressure: $\displaystyle p_{\text{total}} = p_A^\circ x_A + p_B^\circ x_B$

Relative lowering of vapour pressure: $\displaystyle \frac{p^\circ - p}{p^\circ} = x_{\text{solute}}$
Elevation of boiling point: $\displaystyle \Delta T_b = iK_bm$
Depression of freezing point: $\displaystyle \Delta T_f = iK_fm$
Osmotic pressure: $\displaystyle \pi = iCRT$
van't Hoff factor: $\displaystyle i = \frac{\text{observed colligative property}}{\text{calculated colligative property}}$
Degree of dissociation: $\displaystyle \alpha = \frac{i - 1}{n - 1}$
n is the number of ions formed.

Cell potential: $\displaystyle E^\circ_{\text{cell}} = E^\circ_{\text{cathode}} - E^\circ_{\text{anode}}$
Nernst equation: $\displaystyle E = E^\circ - \frac{0.0591}{n}\log Q$
At 298 K.
Gibbs energy: $\displaystyle \Delta G^\circ = -nFE^\circ$
Equilibrium constant: $\displaystyle \log K = \frac{nE^\circ}{0.0591}$
At 298 K.

Resistance: $\displaystyle R = \rho\frac{l}{A}$
Conductivity: $\displaystyle \kappa = \frac{1}{\rho} = \frac{G^*}{R}$
G* is the cell constant, l/A.
Molar conductivity: $\displaystyle \Lambda_m = \frac{\kappa\times1000}{C}$
κ in S cm⁻¹ and C in mol L⁻¹.
Kohlrausch's law: $\displaystyle \Lambda_m^\circ = \nu_+\lambda_+^\circ + \nu_-\lambda_-^\circ$
Strong electrolytes: $\displaystyle \Lambda_m = \Lambda_m^\circ - A\sqrt{C}$
Degree of dissociation: $\displaystyle \alpha = \frac{\Lambda_m}{\Lambda_m^\circ}$

Faraday's first law: $\displaystyle m = ZIt = \frac{EIt}{F}$
E is the equivalent weight, and F = 96500 C/mol.
Faraday's second law: $\displaystyle \frac{m_1}{m_2} = \frac{E_1}{E_2}$

Rate law: $\displaystyle \text{rate} = k[A]^x[B]^y$
Order x + y comes from experiment, not the balanced equation.
Units of k: $\displaystyle (\text{mol L}^{-1})^{1 - n}\,\text{s}^{-1}$
n is the order.

Zero order: $\displaystyle [R] = [R]_0 - kt, \quad t_{1/2} = \frac{[R]_0}{2k}$
First order: $\displaystyle k = \frac{2.303}{t}\log\frac{[R]_0}{[R]}$
First order half-life: $\displaystyle t_{1/2} = \frac{0.693}{k}$
Doesn't depend on initial concentration.

Arrhenius equation: $\displaystyle k = Ae^{-E_a/RT}$
Two temperatures: $\displaystyle \log\frac{k_2}{k_1} = \frac{E_a}{2.303R}\left(\frac{T_2 - T_1}{T_1T_2}\right)$

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