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 only correct answer is:

• D: 450 °C and 200 atmospheres. This choice reflects the high temperature and pressure typically used in the Haber process to maximize ammonia production.

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

If the temperature is decreased, the equilibrium position will shift to the exothermic direction, which in this case is the formation of ammonia. Since the reaction releases heat, lowering the temperature favors the production of ammonia (NH₃) according to Le Chatelier's principle. Thus, more ammonia will be produced as the system attempts to counteract the decrease in temperature.

To investigate the effect of temperature on the equilibrium position of the reaction between compounds A and B, perform the following steps:

1. Preparation: Place the sealed glass tube containing the equilibrium mixture of A (dark brown gas) and B (colourless gas) in the kettle filled with hot water, ensuring the sealed tube does not open.

2. Observation: As the temperature of the mixture increases, observe any color change in the gases present in the sealed tube.

3. Cooling: Once the temperature effect is noted, transfer the sealed tube into an ice bath to rapidly decrease the temperature.

4. Final Observation: After a few minutes, observe any changes in the color of the gases again. Record the results to analyze how the temperature affects the equilibrium position.