Le Chatelier's Principle and Factors Effecting Equilibrium

Le Chatelier's Principle :

Applicable for only reversible reaction
Effect of concentration :
If concentration of reactant ↑ / product ↓ → forward reaction
If concentration of reactant ↓ / product ↑ → backward reaction

Effect of pressure :
Pressure(P) ↑ no. of moles ↓ (or) volume ↓
Pressure(P) ↓ no. of moles ↑ (or) volume ↑

ex :
↑ of P → favours forward reaction
↓ of P → favours backward reaction

Effect of temperature :
↑ of temperature → favours endothermic reaction.
↓ of temperature → favours exothermic reaction.

ex :
↑ T → B.R → Reddish brown ↑
↓ T → exothermic → intensity RB ↓

Haber's process :
N_{2(g)} + 3H_{2(g)} \rightleftharpoons 2NH_{3(g)} ; \Delta H = -92kJ

Temperature (T) : Low T
∴ 725 - 775 K
Catalyst : Fe (or) FeO
promoter :
K_{2}O + Al_{2}O_{3} (or) Molybdenum

Contact process :
2SO_{2(g)} + O_{2(g)} \rightleftharpoons 2SO_{3(g)} ; \Delta H = -189kJ
Pressure : High pressure 1 - 2 atm
Temperature : Optimum temperature, 673 - 723 K
Catalyst : Pt (or) V₂O₅

Degree of dissociation (α) using vapour density :
\alpha = \frac{No. of \ particles \ dissociated}{No.of \ particles \ taken}
\frac{D}{d} = 1 + (n - 1)x \ \Rightarrow \frac{D}{d} - 1 = (n - 1)x
\frac{D - d}{(n - 1)d} = x \ (or) \ \frac{M - m}{m(n - 1)} = x
D = initial vapour density
d = equilibrium vapour density.