The temperature chosen is a compromise between yield and rate. Using a catalyst in the Haber process means that a lower temperature can be used whilst keeping the rate of reaction high.

For AQA GCSE Chemistry, the specific details of how ammonia is made using the Haber process need to be known, as well as an ability to apply the principles on this page to an unfamiliar new ...

Haber on the A award of the Nobel Prize at Stockholm ... soon made it clear that the basis of an important technical process could be found in ammonia synthesis, and further work was undertaken ...