Chemistry · Oct / Nov 2018 · Paper 11 · Question 22

The diagram shows the main stages in the manufacture of an ammonia-based fertiliser. [diagram: N2(g) and H2(g) entering a box labelled 'iron 500 °C 200 atm pressure', arrow to 'separation', arrow to 'fertiliser manufacture'; a recycle loop labelled X returns from separation to the start]

1. AAmmonia is returned to the start of the process to shift the equilibrium towards the product.
2. BThe gases are cooled to cause ammonia to form a liquid.
3. CUnreacted hydrogen only is recycled.
4. DUnreacted hydrogen and nitrogen are recycled.

As printed in the paper