Question

Give reason for the following

Ammonia is un-ionised in the gaseous state but in the aqueous solution is a weak electrolyte.

Answer 1

Ammonia is un-ionized in the gaseous state but in the aqueous solution is a weak electrolyte because of the following reason:

• Ammonia is a covalent compound containing nitrogen and hydrogen atoms of the chemical formula NH₃ therefore in the gaseous state it is un-ionized.
• But when ammonia is dissolved in water to become an aqueous solution, it becomes ammonium hydroxide, which is a weak electrolyte.

$\underset{\mathrm{Ammonia}}{{\mathrm{NH}}_3\left(\mathrm{g}\right)}+\underset{\mathrm{Water}}{{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}\rightleftharpoons \underset{\mathrm{Ammonium}\mathrm{hydroxide}}{{\mathrm{NH}}_4\mathrm{OH}\left(\mathrm{l}\right)}$

$\underset{\mathrm{Ammonium}\mathrm{hydroxide}}{{\mathrm{NH}}_4\mathrm{OH}}\stackrel{\left(\mathrm{aq}\right)}{\rightleftharpoons }\underset{\mathrm{Ammonium}\mathrm{ion}}{{{\mathrm{NH}}_4}^{+}}+\underset{\mathrm{Hydroxide}\mathrm{ion}}{{\mathrm{OH}}^{-}}$

• Ammonium hydroxide is a weak electrolyte, it contain ions as well as undissociated molecules, hence it is a weak electrolyte