Question

Statement: The pH of an aqueous solution of acetic acid remains unchanged on the addition of sodium acetate.
Explanation: The ionisation of acetic acid is suppressed by the addition of sodium acetate.
A. If both assertion and reason are true and reason is the correct explanation of assertion.
B. If both assertion and reason are true but reason is not the correct explanation of assertion.
C. If assertion is true but reason is false.
D. If both assertion and reason are false.

Answer 1

Correct Answer - D
Addition of a small amount of `CH_(3)COONa` to acetic acid increase the pH value because `CH_(3)COONa` is a strong electrolyte and thus ionizes to give `CH_(3)COO^(-) and Na^(+)` ions. Due to common ion effect, it suppresses the ionization of `CH_(3)COOH` which decreases `[H^(+)]` and hence pH value increase.