3 (a) Ammonia is manufactured in the Haber process by the reversible reaction between nitrogen and hydrogen - Edexcel - GCSE Chemistry Combined Science - Question 3 - 2023 - Paper 1

The typical conditions used in the Haber process are a temperature of 450 °C and a pressure of 200 atmospheres. Therefore, the correct row is D.

The purpose of the iron in the Haber process is to act as a catalyst. It increases the rate of the reaction without being consumed in the process, allowing the equilibrium to be reached more quickly.

Decreasing the temperature in an exothermic reaction, such as the formation of ammonia from nitrogen and hydrogen, shifts the position of equilibrium to the right. This is because the system seeks to produce more heat to counteract the decrease in temperature. Thus, more ammonia is produced at lower temperatures.

To investigate how temperature affects the position of equilibrium, one can set up the following experiment:

1. Preparation: Take a sealed glass tube containing a mixture of compounds A (dark brown gas) and B (colourless gas).
2. Heating: Place the glass tube in a kettle filled with hot water to increase the temperature, ensuring that the tube remains sealed.
3. Observation: Record the colour of the gas mixture at different temperatures, noting any changes in the intensity of the brown colour as the temperature increases; this indicates a shift in the equilibrium position.
4. Chilling: To observe the reverse effect, place the tube in an ice bath to decrease the temperature, and again note the changes in colour.
5. Conclusion: By comparing the results from both heating and cooling, one can conclude how temperature affects the equilibrium position of the reaction.