CBSE Class 12 Chemistry Important Formulas All Chapters

Solution

1. Mole fraction (x)

if the number of moles of A and B are nA and nB respectrively, the mole fraction of A and B will be

X_A= X/n_A+n_B , AND  X_B = n_B / n_A+n_B

2. Molarity (M) = Moles of solute/ Volume of solution in litres

3. Moality (m) = Moles of solute / Mass of solvent in kilograms

4. Parts per million (ppm) = Number of parts of the component 106 /Total number of parts of all components of the solution

5. Raoult’s law for a solution of volatile solute in volatile solvent :

p_A = p_A° x_A

p_B = p_B° x_B

Where p_A and p_B are partial vapour pressures of component ‘A’ and component ‘B’ in solution. p_A° and p_B° are vapour pressures of pure components ‘A’ and ‘B’ respectively.

6. Raoults law for a solution of non-volatile solute and volatile solvent :

p °_A – p °_A/ p °_A  = i  n_B /n_A =  i   W_B* M_A / M_B* W_A  (for dilute solution)

Where xB is mole fraction of solute, i is van’t Hoff factor and A A

p °_A – p °_A / p_A °  IS Nrelative lowering of vapour pressure.

Chemical Kinetics

1. Integrated rate law equation for zero order reaction
(a) k = [R]_º[R]/t
Where k is rate constant and [R]₀ is initial molar concentration.

(b) t_1/2 = [R]_º/2k

t_1/2 is half life period of zero order reaction.

2. Integrated rate law equation for first order reaction

(a) k = 2.303/k log [R]_º/[R]

Where k is rate constant, [R]_° is initial molar concentration and [R] is final concentration at time ‘t’.

(b) Half life period (t_1/2) for first order reaction :

t_1/2 = 0.693/k

3. Anhenius epuation

(a) k = A_e –Ea/RT 
Where ‘A’ is frequency factor, Ea is the energy of activation, R is universal gas contant and T is absolute temperature.

^–Ea/_RT gives the fraction of collisions having energy equal to or greater than Ea.

(b) log k₁/k₂ = Ea/ 2.303 R (T₂ - T₁/T₁ - T₂)
Where k₁ is rate constant at temperature T₁ and k₂ is rate constant at temperature T₂.

Please click the link below to download pdf file for CBSE Class 12 Chemistry - Important Formulas all chapters.