Question

Acetic acid dissociates in an equilibrium with acetate ion and proton. When a small amount of HCl is added:

• A. the equilibrium constant will increase
• B. acetate ion concentration decreases
• C. acetate ion concentration increases
• D. the equilibrium constant will decrease

Answer 1

Answer: (B)

Acetic acid is weak acid ,hence it ionizes feebly producing less number of H+ and acetate ions.But HCL is strong acid, hence ionises completely producing large number of H+ions.

Hydrogen ion is common to both acetic acid and HCl. Due to this, concentration of H+ ion in the solution increases.

According to Le-Chatelier’s principle ,acetate ions combine with H+ ions to form undissociated acetic acid.And hence equilibrium get shifted towards left hand side. Thus due to addition of HCl to acetic acid ,ionization of Acetic Acid get suppresed.