It is a colorless gas with pungent smell, highly soluble in H₂O and basic in nature. It liquefies on cooling under pressure to give liquid ammonia (bp. 240K). On heating, it causes intense cooling and hence is used as a refrigerant in ice, factories and cold storages.

It burns in excess of air to give N₂ and H₂O and is oxidized to NO when passed over heat Pt at 1075K .

4NH₃ + 3O₂ ——→ 2N₂ + 6H₂O

It reduces heated CuO to Cu and CI₂ to HCI (which combines with NH₃ to give NH₄CI ).

With excess of CI₂ , it gives NCI₃ . With Br₂ it gives NH₄ Br and N₂ is set free.

NH3 + 3CI2 ——→ NCI3 + 3HCI

Excess

8NH₃ + 3Br₂ ——→ 6NH₄ Br + N₂

With I₂ , it gives nitrogen triiodide ammonia (brown ppt) which is explosive in dry state and decomposes when struck

2NH₃ + 3 I₂ ——→ NH₃.NI₃ + 3HI

8NH₃.NI₃ ——→ 5N₂ + 9I₂ + 6NH₄I

It forms amides with active metals like Na,K etc.

It forms complexes with many substances, e.g.,

[ Ca (NH₃ )₆] CI₂, [ Co ( NH₃)₆ ] CI₂, [ Cu ( NH₃ )₄ ] SO₄,

[ Ag ( NH₃ )₂ ] CI, [ CD ( NH₃ )₄ CI₂ , etc.

Its aqueous solution is weakly basic due to the formation of OH^- ions,

NH₃ + H₂O ———→ NH⁺₄ + OH^-

With sodium hypochlorite in presence of glue or gelatine, excess of ammonia gives hydrazine

2NH₃ + NaOCI ——→ NH₂.NH₂ + NaCI + H₂O

It undergoes self ionization in liquid state and acts as a solvent. 2NH3 ———→ NH⁺₄ + NH_^-2

Many polar compounds are soluble in liquid ammonia.

With Nessler’s reagent (an alkaline solution of K₂HgI₄ ) , ammonia and ammonium salts give a brown precipitate due to the formation of Millon’s base.

K₂HgI₄ 2KI + HgI₂

HgI₂ + 2NH₃ ——→ I - Hg - NH₂ + NH₄ I

2NH₂ - Hg - I + H₂O ——→ NH₂ - Hg - O - Hg - I + NH₄I

or 2K₂HgI₄ + NH₃ + 3KOH ——→ H₂N - Hg - O Hg - I 7KI + 2H₂O

or

It is used as a refrigerant and in the manufacture of fertilizers.

STRUCTURE OF NH₃: The N atom in NH₃ is sp³-hybridized containing a lone pair of electrons due to which the H - N - H bond angle is 107.5^o . As a result NH₃ molecule is pyramidal.