Describe how phosphate rock is treated to produce soluble salts for fertilisers.

Phosphate rock is treated with acids such as nitric acid, sulfuric acid, or phosphoric acid to produce soluble salts. This treatment converts the insoluble phosphate into soluble forms that can be absorbed by plants.

A strong answer should directly address the approved learning objective to recall that phosphate rock is obtained by mining but cannot be used directly as a fertiliser. (Chemistry only). This question belongs to Production and uses of NPK fertilisers 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.