Question

Consider the reaction shown. Using your knowledge of relative acid-base strengths and equilibrium, determine what you can about the size of K_c for the reaction.

HOCl(aq) + ClO₃^-(aq) <=> OCl^-(aq) + HClO₃(aq)

Answer 1

Solution: (Kc < 1)

In the given acid- base reaction,

HOCl(aq) + ClO3-(aq) ==  OCl-(aq) + HClO3(aq)

Kc = [OCl-] [HClO3] / [HOCl] [ClO3-]

>>HOCl is a weak acid hence, its conjugate base OCl- is strong base while HClO3 is a strong acid hence, it's conjugate base ClO3- is a weak base.

Thus, a weak acid and weak base reaction can not go towards completion, hence the concentrations of HOCl and ClO3- is high, therefore quilibrium is always shifted towards reactant side.

Hence, Kc < 1