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Science

Making ammonia

The Haber process

The raw materials for this process are hydrogen and nitrogen:

  • hydrogen is obtained by reacting natural gas with steam, or from cracking oil fractions
  • nitrogen is obtained from the air.

Air is 78 per cent nitrogen and nearly all the rest is oxygen. When hydrogen is burned in air, the oxygen combines with the hydrogen, leaving nitrogen behind.

In the Haber process, nitrogen and hydrogen react together under these conditions:

  • a high temperature - about 450ºC
  • a high pressure
  • an iron catalyst.

In addition, any unreacted nitrogen and hydrogen are recycled.

The reaction is reversible. In a chemical equation, the symbol Equilibrium symbol is used instead of an ordinary arrow if the reaction is reversion:

nitrogen + hydrogen Equilibrium symbol ammonia

N2 + 3H2Equilibrium symbol 2NH3

The flow chart shows the main stages in the Haber process.

 Hydrogen is extracted from the reaction between methane and steam. Nitrogen is extracted from the combustion of hydrogen in air. Hydrogen and nitrogen are combined at a pressure of 200 atmospheres and a temperature of 450°C, with iron as a catalyst, to produce ammonia

The Haber process for making ammonia

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