Answer to Question #106208 in Physical Chemistry for Nikesh

Question

Explain the effect of common ions on the ionisation equilibria of weak acids with
the help of a suitable example.

Answer 1

СH₃COOH+HOH=CH₃COO^-+H₃O⁺ - weak acid equilibria

СH₃COONa=CH₃COO^-+Na⁺ - common acetate ion

As we have more acetate ions added to the system, the total equilibria would be changed to reduce this influence. That's why the dissosiation of the weak acid would be reduced to form more СH₃COOH molecules.