Gas chemistry - (CCEA)Ammonia - Higher tier

Physical properties

Ammonia, NH₃, is a colourless, pungent gas that is soluble in water and less dense in air.

Test for ammonia

Method: Dip a glass rod in concentrated hydrochloric acid and put this in a sample of the gas.

Result: If ammonia is present, a white ‘smoke’ of ammonium chloride is observed.

Uses of ammonia

Ammonia is used to produce fertilisers by reacting it with acids such as hydrochloric acid and nitric:

NH₃ + HCl → NH₄Cl

NH₃ + HNO₃ → NH₄NO₃

The ammonium salts (ammonium chloride, NH₄Cl, and ammonium nitrate, NH₄NO₃) are very soluble in water, so they can dissolve in soil water and be absorbed by plants.