Question

Consider the redox reaction 2Fe^2+(aq) + H2O2(aq) + 2H^+(aq) ⟷ 2Fe^3+(aq) + 2H2O(l). If a catalyst is added to the reaction mixture at equilibrium, will the concentration of Fe^3+ increase, decrease or remain the same? Justify your answer mathematically.

Answer 1

When a catalyst is added to a reaction mixture at equilibrium, it increases the rate of both the forward and reverse reactions equally. However, it does not change the position of the equilibrium or the equilibrium constant  K . In this redox reaction, the equilibrium constant K can be expressed as:K = [Fe^3+]^2[H2O]^2 /  [Fe^2+]^2[H2O2][H^+]^2 Since the catalyst does not change the value of K, the ratio of the concentrations of the products to the reactants remains the same. Therefore, the concentration of Fe^3+ will remain the same when a catalyst is added to the reaction mixture at equilibrium.