Ammonia and nitric acid react to produce the salt, ammonium nitrate. Ammonium ions and nitrate ions both contain nitrogen. Suggest one use of ammonium nitrate.

Ammonium nitrate (NH₄NO₃) is a salt that is rich in nitrogen, containing it in both the ammonium ion (NH₄⁺) and the nitrate ion (NO₃⁻). Nitrogen is an essential element for plant growth, as it is a key component of proteins and DNA. Soils can often be deficient in nitrogen, limiting crop yield. Therefore, nitrogen-based compounds like ammonium nitrate are manufactured on a large scale and used as fertilisers to add nitrogen to the soil, promoting healthy plant growth and increasing food production.