Le Chatelier’s Principle:
It states that if a system in equilibrium is subjected to a change of temperature pressure or concentration then the equilibrium shift in such a way that the effect of the changed condition is nullified. Thus, according to Le Chatelier’s Principle –
i. Effect of Temperature:
If the temperature is raised, the reaction will proceed in a direction in which some heat can be destroyed so that the temperature of the system remains constant. Thus, an increase in temperature shifts the equilibrium in the forward direction of those reactions which proceed with the absorption of heat.
The backward direction of those reactions proceeds with the evolution of heat.
ii. Effect of Pressure:
If the pressure is increased, a reaction will take place in a direction which will bring about a lowering of pressure. This implies that the equilibrium will shift in a direction which produces a smaller number of gas molecules.
The forward reaction is favoured with an increase of pressure.
It is important to note that the change in pressure has no effect on equilibrium if the total volume of the reactant and the products are the same.
iii. If the concentration of reactants is increased or the product is removed, the reaction will take place in the forwarding direction.
iv. In a reversible reaction a catalyst helps in achieving the equilibrium state quickly without shifting in one direction or the other.