The Haber process

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.

Hydrogen from natural gas and nitrogen from air are combined at a pressure of 200 atmospheres and a temperature of 450 degrees Celsius using an iron catalyst, to produce ammoniaThe main stages in the Haber process

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

Worked example


Explain why iron is used in the Haber process.

Iron is a catalyst for the reaction. It increases the rate of the reaction without being used up in the reaction.


Explain why the unreacted hydrogen and nitrogen are recycled.

Recycling the unused reactants saves money and increases the effective (overall) yield.