State Le-Chatelier's principle. (b) Explain the effect of temperature and pressure on the equilibrium equation.

Question

(a) State Le-Chatelier's principle. 

(b) Explain the effect of temperature and pressure on the equilibrium equation. 

(c) What is a buffer solution? Give an example.

Answer 1

(a) Correct statement 

(b) When temperature is increased at equilibrium, endothermic reaction proceeds in forward direction and an exothermic reaction proceeds in backward direction. Pressure has no effect on equilibrium when equal number of gaseous molecules of reactants and products are present and increase of pressure shifts the equilibrium in the direction with lesser number of gaseous molecules. 

(c) The solution which resists change in pH on addition of small amount of acid or alkali.

Detailed Answer : 

(a) If a chemical reaction at equilibrium is subjected to small changes in P, T or concentration, the equilibrium shifts in a direction so to undo the effect of the change. 

(b) Effect of temperature - Increase of Temperature 

(i) For exothermic reactions, equilibrium shifts in backward direction. 

(ii) For endothermic reactions, equilibrium shifts in forward direction. 

Effect of Pressure - Increase of pressure shifts the equilibrium in the direction with lesser number of gaseous molecules and no effect of pressure in case of equal number of molecules of reactants and products.

(c) Example of Buffer Solution : CH₃COOH + CH₃COONa (Acidic buffer solution) NH₄OH + NH₄Cl (Basic buffer solution)