The Haber Process and Fertilisers - AQA GCSE Chemistry

Introduction to Fertilisers

• Fertilisers are essential for the healthy growth of crops.
• They can be made in laboratories or on a larger scale by the chemical industry.
• Relevant to Chemistry (Single Science) and the topic of using resources.

The Haber Process

• Purpose: The Haber process is an industrial method for producing ammonia, which is crucial for making fertilisers, explosives, and dyes.

• Chemical Reaction: A reversible reaction between nitrogen (N2) and hydrogen (H2) to produce ammonia (NH3).

  [ N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g) ]

• Dynamic Equilibrium: The reaction can reach a state where the forward and backward reactions occur at the same rate, maintaining constant concentrations.

Main Stages of the Haber Process

1. Extraction of Gases
   • Nitrogen is extracted from the air.
   • Hydrogen is obtained from natural gas.
2. Pressurization
   • The gases are pressurized to 200 atmospheres.
3. Heating
   • The pressurized gases are heated to 450 degrees Celsius.
4. Catalysis
   • The gases pass through a tank containing an iron catalyst to speed up the reaction.
5. Cooling and Collection
   • The reaction mixture is cooled so that ammonia liquefies and can be collected.
6. Recycling
   • Unreacted nitrogen and hydrogen are recycled to improve efficiency.

Worked Examples

• Role of Iron: Iron is used as a catalyst to increase the reaction rate without being consumed.
• Recycling Unreacted Gases: Recycling saves money and increases the overall yield of ammonia.

Conclusion

• The Haber Process is vital for industrial ammonia production, which feeds into the creation of essential agricultural and industrial products.

Further Reading and Resources

• Sustainable development, water management, reducing resource use, and sample exam questions.
• Relevant links include exam practice, chemistry jobs, and resources from the Royal Society of Chemistry and Science Museum.