Question

$N{H}_{4}OH$ is weak base but it becomes still weaker in the aqueous solution of :

• A. 0.1 M HCl
• B. 0.1 M $N{H}_{4}Cl$
• C. 0.1 M $H_{2}S{O}_4$
• D. 0.1 M $C{H}_{3}COOH$

Answer 1

The correct option is B 0.1 M $N{H}_{4}Cl$

Common ion effect is observed when a solution of weak electrolyte is mixed with a solution of strong electrolyte which provides an ion common to that provided by a weak electrolyte.

Ammonium hydroxide is a weak electrolyte and ammonium chloride is a strong electrolyte. Ammonium chloride provides ammonium ion which is common to that provided by ammonium hydroxide.

Thus the pair $N{H}_{4}OH+N{H}_{4}Cl$ shows common ion effect. Ammonium chloride suppresses the ionization of ammonium hydroxide.

Hence, ammonium hydroxide becomes still weaker in the presence of an aqueous solution of ammonium chloride.