ISC Class 12 Chemistry Formulas
Every ISC Class 12 Chemistry formula that the Prashnika chemistry numericals calculator knows, by topic: 38 formulas with their letters and units, the same ones used to check the answers on this site. Use it as a revision sheet, then open the Chemistry numericals calculator to work a numerical out.
Solutions: 13 formulas
| Formula | Equation | Letters and their units |
|---|---|---|
| Number of moles | $n = \dfrac{w}{M}$ | $n$ (mol), $w$ (g), $M$ (g mol⁻¹) |
| Molality | $m = \dfrac{w_2}{M_2\,w_1}$ | $m$ (mol kg⁻¹), $w_2$ (g), $M_2$ (g mol⁻¹), $w_1$ (g) |
| Molarity | $C = \dfrac{n}{V}$ $n = \dfrac{w_2}{M_2}$ | $C$ (mol L⁻¹), $n$ (mol), $V$ (L), $w_2$ (g), $M_2$ (g mol⁻¹) |
| Mole fraction of the solute | $x_2 = \dfrac{n_2}{n_1 + n_2}$ $n_1 = \dfrac{w_1}{M_1}$ $n_2 = \dfrac{w_2}{M_2}$ | $x_2$ (no unit), $n_1$ (mol), $n_2$ (mol), $w_1$ (g), $M_1$ (g mol⁻¹), $w_2$ (g), $M_2$ (g mol⁻¹) |
| Relative lowering of vapour pressure = mole fraction of the solute | $\dfrac{p^\circ - p}{p^\circ} = \dfrac{in_2}{n_1 + n_2}$ $n_1 = \dfrac{w_1}{M_1}$ $n_2 = \dfrac{w_2}{M_2}$ | $p^\circ$ (mmHg), $p$ (mmHg), $i$ (no unit), $n_1$ (mol), $n_2$ (mol), $w_1$ (g), $M_1$ (g mol⁻¹), $w_2$ (g), $M_2$ (g mol⁻¹) |
| Relative lowering of vapour pressure, dilute solution | $\dfrac{p^\circ - p}{p^\circ} = \dfrac{iw_2\,M_1}{M_2\,w_1}$ | $p^\circ$ (mmHg), $p$ (mmHg), $i$ (no unit), $w_2$ (g), $M_1$ (g mol⁻¹), $M_2$ (g mol⁻¹), $w_1$ (g) |
| Vapour pressure of a mixture of two liquids | $p = x_Ap_A^\circ + x_Bp_B^\circ$ $x_A + x_B = 1$ | $p$ (mmHg), $x_A$ (no unit), $x_B$ (no unit), $p_A^\circ$ (mmHg), $p_B^\circ$ (mmHg) |
| Elevation of boiling point | $\Delta T_b = iK_bm$ $m = \dfrac{w_2}{M_2\,w_1}$ | $\Delta T_b$ (K), $i$ (no unit), $K_b$ (K kg mol⁻¹), $m$ (mol kg⁻¹), $w_2$ (g), $M_2$ (g mol⁻¹), $w_1$ (g) |
| Depression of freezing point | $\Delta T_f = iK_fm$ $m = \dfrac{w_2}{M_2\,w_1}$ | $\Delta T_f$ (K), $i$ (no unit), $K_f$ (K kg mol⁻¹), $m$ (mol kg⁻¹), $w_2$ (g), $M_2$ (g mol⁻¹), $w_1$ (g) |
| Osmotic pressure | $\pi = iCRT$ $C = \dfrac{w_2}{M_2\,V}$ | $\pi$ (atm), $i$ (no unit), $C$ (mol L⁻¹), $R$ (L atm K⁻¹ mol⁻¹), $T$ (K), $w_2$ (g), $M_2$ (g mol⁻¹), $V$ (L) |
| van 't Hoff factor from molar masses | $i = \dfrac{M_{normal}}{M_{observed}}$ | $i$ (no unit), $M_{normal}$ (g mol⁻¹), $M_{observed}$ (g mol⁻¹) |
| Degree of dissociation from i | $\alpha = \dfrac{i - 1}{\nu - 1}$ | $\alpha$ (no unit), $i$ (no unit), $\nu$ (no unit) |
| Degree of association from i | $\alpha = \dfrac{1 - i}{1 - \dfrac{1}{\nu}}$ | $\alpha$ (no unit), $i$ (no unit), $\nu$ (no unit) |
Electrochemistry: 14 formulas
| Formula | Equation | Letters and their units |
|---|---|---|
| Standard emf of a cell | $E^\circ_{cell} = E^\circ_{cathode} - E^\circ_{anode}$ | $E^\circ_{cell}$ (V), $E^\circ_{cathode}$ (V), $E^\circ_{anode}$ (V) |
| Nernst equation at 298 K | $E = E^\circ - \dfrac{0.0591}{n}\,\log_{10}\,Q$ | $E$ (V), $E^\circ$ (V), $n$ (no unit), $Q$ (no unit) |
| Nernst equation at temperature T | $E = E^\circ - \dfrac{2.303\,RT}{nF}\,\log_{10}\,Q$ | $E$ (V), $E^\circ$ (V), $R$ (J K⁻¹ mol⁻¹), $T$ (K), $n$ (no unit), $F$ (C mol⁻¹), $Q$ (no unit) |
| Gibbs energy from emf | $\Delta G = -nFE$ | $\Delta G$ (J mol⁻¹), $n$ (no unit), $F$ (C mol⁻¹), $E$ (V) |
| Gibbs energy from the equilibrium constant | $\Delta G = -2.303\,RT\log_{10}\,K$ | $\Delta G$ (J mol⁻¹), $R$ (J K⁻¹ mol⁻¹), $T$ (K), $K$ (no unit) |
| Equilibrium constant from emf at 298 K | $\log_{10}\,K = \dfrac{nE^\circ}{0.0591}$ | $K$ (no unit), $n$ (no unit), $E^\circ$ (V) |
| Cell constant | $G^* = \dfrac{l}{A}$ | $G^*$ (cm⁻¹), $l$ (cm), $A$ (cm²) |
| Conductivity from resistance | $\kappa = \dfrac{G^*}{R_{cell}}$ | $\kappa$ (S cm⁻¹), $G^*$ (cm⁻¹), $R_{cell}$ (ohm) |
| Molar conductivity | $\Lambda_m = \dfrac{\kappa}{C}$ | $\Lambda_m$ (S cm² mol⁻¹), $\kappa$ (S cm⁻¹), $C$ (mol L⁻¹) |
| Degree of dissociation from molar conductivities | $\alpha = \dfrac{\Lambda_m}{\Lambda_m^\circ}$ | $\alpha$ (no unit), $\Lambda_m$ (S cm² mol⁻¹), $\Lambda_m^\circ$ (S cm² mol⁻¹) |
| Dissociation constant of a weak electrolyte | $K_a = \dfrac{C\alpha^{2}}{1 - \alpha}$ | $K_a$ (mol L⁻¹), $C$ (mol L⁻¹), $\alpha$ (no unit) |
| Kohlrausch's law: Lm0 = L1 + L2 - L3 | $\Lambda_m^\circ = L_1 + L_2 - L_3$ | $\Lambda_m^\circ$ (S cm² mol⁻¹), $L_1$ (S cm² mol⁻¹), $L_2$ (S cm² mol⁻¹), $L_3$ (S cm² mol⁻¹) |
| Faraday's first law | $w = \dfrac{MQ}{nF}$ $Q = It$ | $w$ (g), $M$ (g mol⁻¹), $Q$ (C), $n$ (no unit), $F$ (C mol⁻¹), $I$ (A), $t$ (s) |
| Faraday's second law | $\dfrac{w_1}{w_2} = \dfrac{\dfrac{M_1}{n_1}}{\dfrac{M_2}{n_2}}$ | $w_1$ (g), $w_2$ (g), $M_1$ (g mol⁻¹), $n_1$ (no unit), $M_2$ (g mol⁻¹), $n_2$ (no unit) |
Kinetics: 7 formulas
| Formula | Equation | Letters and their units |
|---|---|---|
| First-order integrated rate law | $k = \dfrac{2.303}{t}\,\log_{10}\left(\dfrac{A_0}{A}\right)$ | $k$ (s⁻¹), $t$ (s), $A_0$ (any unit), $A$ (any unit) |
| Half-life, first order | $t_{1/2} = \dfrac{0.693}{k}$ | $t_{1/2}$ (s), $k$ (s⁻¹) |
| Zero-order integrated rate law | $A = A_0 - kt$ | $A$ (mol L⁻¹), $A_0$ (mol L⁻¹), $k$ (mol L⁻¹ s⁻¹), $t$ (s) |
| Half-life, zero order | $t_{1/2} = \dfrac{A_0}{2\,k}$ | $t_{1/2}$ (s), $A_0$ (mol L⁻¹), $k$ (mol L⁻¹ s⁻¹) |
| Second-order integrated rate law | $\dfrac{1}{A} - \dfrac{1}{A_0} = kt$ | $A$ (mol L⁻¹), $A_0$ (mol L⁻¹), $k$ (L mol⁻¹ s⁻¹), $t$ (s) |
| Arrhenius equation | $k = Ae^{\dfrac{-E_a}{RT}}$ | $k$ (s⁻¹), $A$ (s⁻¹), $E_a$ (J mol⁻¹), $R$ (J K⁻¹ mol⁻¹), $T$ (K) |
| Arrhenius equation at two temperatures | $\log_{10}\left(\dfrac{k_2}{k_1}\right) = \dfrac{\dfrac{E_a}{2.303\,R}\,\left(T_2 - T_1\right)}{T_1\,T_2}$ | $k_2$ (any unit), $k_1$ (any unit), $E_a$ (J mol⁻¹), $R$ (J K⁻¹ mol⁻¹), $T_1$ (K), $T_2$ (K) |
Solid State: 4 formulas
| Formula | Equation | Letters and their units |
|---|---|---|
| Density of a unit cell | $\rho = \dfrac{zM}{a^{3}\,N_A}$ | $\rho$ (g cm⁻³), $z$ (no unit), $M$ (g mol⁻¹), $a$ (cm), $N_A$ (mol⁻¹) |
| Simple cubic: edge and radius | $a = 2\,r$ | $a$ (pm), $r$ (pm) |
| Body-centred cubic: edge and radius | $\sqrt{3}\,a = 4\,r$ | $a$ (pm), $r$ (pm) |
| Face-centred cubic: edge and radius | $a = 2\,\sqrt{2}\,r$ | $a$ (pm), $r$ (pm) |
Constants the calculator fills in for you
| Letter | Constant | Value |
|---|---|---|
| R | gas constant | 8.314 J K⁻¹ mol⁻¹ |
| F | faraday | 96500 C mol⁻¹ |
| NA | Avogadro’s number | 6.022e23 mol⁻¹ |
| e | charge of an electron | 1.6e-19 C |
| h | Planck’s constant | 6.6e-34 J s |
| c | speed of light | 3e8 m s⁻¹ |
| eps0 | permittivity of free space | 8.85e-12 C² N⁻¹ m⁻² |
| mu0 | permeability of free space | 1.2566e-6 T m A⁻¹ |
| k | 1/(4πε₀) | 9e9 N m² C⁻² |
| me | mass of an electron | 9.1e-31 kg |
| mp | mass of a proton | 1.67e-27 kg |
| mn | mass of a neutron | 1.008665 u |
| mH | mass of a hydrogen atom | 1.007825 u |
| c2 | c² in energy units | 931.5 MeV u⁻¹ |
| g | acceleration due to gravity | 9.8 m s⁻² |
The values ISC papers use; if a question prints its own value, type that instead.
Common questions
How many ISC Class 12 Chemistry formulas are on this page?
38 formulas, grouped by topic. Each has its equation or equations and the letters it uses with their units.
Can I use these Chemistry formulas to solve numericals?
Yes: the Chemistry numericals calculator on Prashnika takes any of them, converts the units you type and shows the working in SI units.
Do the formulas include derivations?
No. This page is the list to revise from; the derivations are asked in the paper as separate questions, which you can practise from the chapter pages.
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Last checked 2026-10-16.