Question

What is the action of litmus on dry ammonia gas and solution of ammonia gas in water?

Answer 1

1. As we know, in an acidic medium the color of blue litmus paper turns red and in a basic medium, it turns red to blue.
2. Litmus paper does not show any action in reacting with dry ammonia (NH₃) because it does not release any OH^- ions.
3. Whereas litmus paper show action in reacting with a solution of ammonia in water as it releases free OH^- ions and forms ammonium ion (NH⁺₄) which turns red litmus paper to blue and acts as a base.

Chemical Reaction involved when ammonia gas is added into the water:

${\mathrm{NH}}_3\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\stackrel{}{\rightleftharpoons }{\mathrm{NH}}_4^{+}\left(\mathrm{aq}\right)+{\mathrm{OH}}^{-}\left(\mathrm{aq}\right)$

Therefore, litmus paper only shows action in a solution of ammonia in water, it turns red litmus paper to blue.