Making ammonia

• Ammonia is an important industrial product used to make fertilisers, explosives and dyes. It is manufactured using the Haber process.

• This involves a reversible reaction between nitrogen and hydrogen:

  • N2(g) + 3H2(g) ⇌ 2NH3(g)

  • The reaction can reach a dynamic equilibrium.

In the Haber process:

1. nitrogen (extracted from the air) and hydrogen (obtained from natural gas) are pumped through pipes

2. the pressure of the mixture of gases is increased to 200 atmospheres

3. the pressurised gases are heated to 450°C and passed through a tank containing an iron catalyst

4. the reaction mixture is cooled so that ammonia liquefies and can be removed

5. unreacted nitrogen and hydrogen are recycled