Describe the role of an iron catalyst in the Haber process.

The iron catalyst in the Haber process speeds up the reaction between nitrogen and hydrogen to form ammonia without being consumed in the reaction. It lowers the activation energy required for the reaction, allowing it to occur at a lower temperature and increasing the rate of ammonia production.

A strong answer should directly address the approved learning objective to describe ammonia formation as a reversible reaction. (Chemistry only). This question belongs to The Haber process within The Haber process and the use of NPK fertilisers, so the response should use that exact curriculum context rather than a generic statement. The answer is correct when it names the key idea, explains the link to chemistry only, and keeps the wording specific to AQA GCSE revision.