What is the main purpose of treating phosphate rock with acids in fertiliser production?

The correct option is To produce soluble salts. This answer is correct because it matches the approved learning objective to recall the names of salts made when phosphate rock reacts with nitric acid, sulfuric acid and phosphoric acid. (Chemistry only) in the subtopic Production and uses of NPK fertilisers.

The correct option is To produce soluble salts. To produce soluble salts is correct because it directly supports the approved learning objective to recall the names of salts made when phosphate rock reacts with nitric acid, sulfuric acid and phosphoric acid. (Chemistry only). This belongs to the subtopic Production and uses of NPK fertilisers within The Haber process and the use of NPK fertilisers, so the explanation must stay tied to that curriculum context. The other options are incorrect because they either do not answer this learning objective, use a vague statement, or move away from Production and uses of NPK fertilisers.