The Haber process - higher tier
Making ammonia
Ammonia is an important industrial product used to make fertilisers, explosives and dyes. It is manufactured using the The industrial chemical process that makes ammonia by reacting nitrogen and hydrogen together.. This involves a A chemical reaction which can go both ways, so that products can turn back into reactants. between nitrogen and hydrogen:
N2(g) + 3H2(g) 鈬 2NH3(g)
The reaction can reach a A dynamic equilibrium is one in which the rate of the forward reaction equals the rate of the reverse reaction and the concentrations of the reactants and products remain constant.
In the Haber process:
- Nitrogen (extracted from the air) and hydrogen (obtained from natural gas) are pumped through pipes
- A compressor increases the gas pressure to 200 atmospheres
- The pressurised gases are heated to 450掳C and passed through a reaction chamber containing an iron A substance that increases the rate of a chemical reaction without being used up. to speed up the reaction
- The reaction mixture is cooled so that ammonia liquefies and can be removed
- Unreacted nitrogen and hydrogen are recycled
The conditions are chosen to ensure the process of making ammonia is as profitable as possible.
Question
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.
Question
State the reaction conditions used in the Haber process.
A pressure of 200 atmospheres. A temperature of 450掳C. An iron catalyst.
The equilibrium position
The equilibrium position of a reversible reaction is a measure of the concentrations of the reactants and products at equilibrium. Using the Haber process as an example:
N2(g) + 3H2(g) 鈬 2NH3(g)
The equilibrium position is:
- to the left if the concentrations of N2 and H2 are greater than the concentration of NH3
- to the right if the concentration of NH3 is greater than the concentrations of N2 and H2