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.