Question

State why an aq. soln. of NH₃

1. turns red litmus blue

2. is a weak base and a weak electrolyte.

Answer 1

1. Ammonia on dissolving in water furnishes ammonium (NH₄⁺) ions and hydroxyl (OH^–) ions. The presence of OH^– turns the red litmus blue.

2. When ammonia dissolves in water, it forms ammonium hydroxide. The ammonium hydroxide dissociates to NH₄⁺ ions and OH^– ions.

However, the degree of dissociation of ammonium hydroxide molecules is very low. Thus, due to the presence of few OH^- ions it is a weak base, as well as weak electrolyte.