Question

Dissociation of HCN is suppressed by the addition of HCl. Explain.

Answer 1

The weak acid HCN is dissociated as follows :

The dissociation constant K_a is represented as,

When HCl is added, it increases the concentration of H₃O⁺, hence in order to keep the ratio constant, then by Le Chatelier’s principle, the equilibrium is shifted from right to left, suppressing the dissociation of HCN.