What is the effect of increasing the concentration of a reactant in a reaction mixture at equilibrium?
Solution: Here, we are going to discuss the effect of increasing the concentration in a reaction mixture at equilibrium.
Le Chatelier’s principle predicts that when the concentration of any of the reactants or products in a reaction at equilibrium is changed, the composition of the equilibrium mixture changes so as to minimize the effect of concentration change.
Thus, increasing the concentration of a reactant in a reaction mixture at equilibrium will shift the reaction in the direction that consumes the added substance, i.e., the equilibrium shifts in right(forward) direction.
Let us consider the reaction,
H2(g) + I2(g) ⇄ 2HI(g)
If H2 is added to the reaction mixture at equilibrium, then the equilibrium of the reaction is disturbed. In order to restore it, the reaction proceeds in a direction wherein H2 is consumed, i.e., more of H2 and I2 react to form HI and finally the equilibrium shifts in right(forward) direction. This is in accordance with the Le Chatelier’s principle which implies that in case of addition of a reactant/product, a new equilibrium will be set up in which the concentration of the reactant / product should be less than what it was after the addition but more than what it was in the original mixture.