Chemical Properties of Ammonia Chemistry Notes

Chemical Properties of Ammonia Chemistry Notes

Chemical Properties of Ammonia :

Chemical properties of ammonia are as follows:

Precipitation reactions of aqueous ammonia: It precipitates metal hydroxides from aqueous solutions of metallic salts.

Formation of complexes : Ammonia can form complexes with some cations like Ag²⁺, Cu²⁺, Ca²⁺, Hg²⁺, Zn²⁺ etc. The envolved reactions are as follows:

If in above reaction NH₄ OH solution is taken in excess then white precipitate dissolves in solution and a complex is formed .

Ammonia acts as a Lewis base due to the presence of lone pair of electrons on the nitrogen atom. So ammonia can form co-ordinate bond with transition metal cations and thus forming a complex. In complex ammonia behave as ligand.

Oxidation : In presence of catalyst ammonia is oxidised into nitric oxide (NO).

This reaction is used in Ostwald’s process.

In presence of oxidising agents like CuO, NaClO, CaOCl₂ etc. ammonia is oxidised into dinitrogen. For example.

3CuO + 2NH₃ → 3 Cu + N₂ + 3H₂O
3Ca(OCl)₂ + 4NH₃ → 2N₂ + 3CaC₂ + 6H₂O
3Br₂ + 8NH₃ → N₂ + 6NH⁴ Br

Reaction with halogens : Halogen reacts with ammonia in different ways.

With excess Cl₂ Nitrogen trichloride is formed.

With excess NH₃ : Ammonium chloride and nitrogen are formed.

With Br₂: Ammonium bromide is formed

With I₂ : Nitrogen tri-iodide ammoniate (brown ppt) is obtained.

NH₃ NI₃ acts as an explosive. In dried state when it is either rubbed or struck then it explodes with a loud noise.

Reducing Nature : Ammonia acts as reducing agent. It reduces heavier metal oxides into metals.

Reaction with CO₂ : Ammonia reacts with carbon dioxide and forms ammonium carbonate which decomposes into urea.

Urea acts as fertilizer.

Decomposition : On heating above 500°C or by passing electric arc through ammonia, it decomposes into dihydrogen and dinitrogen.

Liquid ammonia as a solvent: Like water liquid ammonia is also self ionised.
NH₃ + NH₃ → NH₄⁺ + NH₂^–

Therefore liquid ammonia is used as non-aqueous solvent for dissolving many polar compounds.

Basic Nature : Ammonia behave as base. It reacts with acid to form salts. It turns moist red litmus blue.

Reaction with metals : Ammonia gas when passed over molten sodium or potassium metal at 575 K then it forms corresponding amides and liberates dihydrogen.

Reaction with Nessler’s reagent : Ammonia reacts with Nessler’s reagent (alkaline solution of KHgl.) and give a brown precipitate due to the formation of iodide of Millon’s base.

Reaction with sodium hypochlorite : Aqueous ammonia taken excess when treated with sodium hypochlorite in presence of glue or gelatine, then hydrazine is formed.

Chemistry Notes