Consider the nitration of bezene using mixed conc of and . If a large amount of is added to the mixture, tne rate of nitration will be
Effect of concentration change on equilibrium -
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. If we add reactant, the equilibrium shift towards right.
In the nitration of benzene in the presence of conc. H2SO4 and HNO3, benzene is formed.
If a large amount of is added to this mixture more HSO4- ion furnishes and hence the concentrate of electrophile decreases, rate of electrophile aromatic reaction slows down.