Ammonia

Ammonia is an important chemical compound having formula NH₃. It is prepared from hydrogen and nitrogen by Haber process.

In Haber process first of all nitrogen and hydrogen gases are dried and mixed in the ratio of 1:3 by volume. The mixture is then passed over iron catalyst at a temperature of 450°C – 500°C and 200 – 300 atmospheric pressure. The catalyst is mixed with some other substances such as aluminium oxide (Al₂O₃) and potassium oxide (K₂O) which act as promoters. A promoter is a substance which increases the efficiency of a catalyst. Finally, the reaction mixture is cooled to below 0°C to separate the liquid ammonia from unreacted hydrogen and nitrogen gases.

N₂     +     3H₂     →     2NH₃
(Nitrogen + Hydrogen → Ammonia)

Physical Properties of Ammonia

1. It is a colourless gas and has a pungent smell.
2. It can be easily liquefied.
3. It is lighter than air.
4. It is highly soluble in water.

Chemical Properties of Ammonia

Ammonia turns red litmus blue. This means that ammonia is alkaline in nature.

1. Reaction of Ammonia with Water

Ammonia reacts with water to form ammonium hydroxide.

NH₃     +     H₂O     →     NH₄OH
(Ammonia + Water → Ammonium hydroxide)

2. Reaction of Ammonia with HCl

When a rod of glass dipped in concentrated hydrochloric acid is introduced in a jar containing ammonia, ammonium chloride is formed in the form of dense white fumes.

NH₃         +         HCl     →         NH₄Cl
(Ammonia + Hydrochloric acid  → + Ammonium chloride)

3. Reducing action of Ammonia

Ammonia is a good reducing agent. Thus, it can reduce metal oxides in metals. For example, copper oxide is reduced to copper metal after reacting with ammonia.

3CuO     +       2NH₃    →   3Cu     +     3H₂O     +     N₂
(Copper oxide + Ammonia → Copper metal + Water + Nitrogen)

4. Catalytic Oxidation of Ammonia

When ammonia is mixed with oxygen and passed over catalyst platinum and heated to 800°C, it is oxidized to nitric oxide.

4NH₃     +     5O₂     →     4NO     +     6H₂O
(Ammonia + Oxygen → Nitric oxide + Water)

Uses of Ammonia

1. The major use of ammonia is in the manufacture of fertilizers such as ammonium nitrate and ammonium sulphate.
2. Hydrogen is used in the manufacture of ammonia by Haber’s process.
3. Various types of dyes, explosives, household cleaners and nylon are prepared from ammonia.
4. It is also used in the manufacture of nitric acid.

Test your understanding and answer these questions:

1. What is haber process?