Question

Dry ammonia gas has no action on litmus papaer, but a solution of ammonia in water turns red litmus paper blu. Why is it so?

Answer 1

Dry ammonia does not contain OH^- ions so id does not have any effect on red litmus paper.

Ammonia reacts with water to form ammonium hydroxide. Ammonium hydroxide is a base and hence it turns red litmus blue.

NH₃ (g) + H₂O (l) → NH₄OH (aq)

So now in moist form it can furnish OH^- and it can turns red litmus paper blue