Chemistry · May / June 2025 · Paper 11 · Question 40

Samples of two compounds, P and Q, are tested. The result of each test is shown. | test | P | Q | |---|---|---| | add dilute hydrochloric acid | gas given off that turns limewater milky | no observable change | | acidify with dilute nitric acid then add aqueous barium nitrate | no precipitate forms | white precipitate | | add aqueous sodium hydroxide | no observable change | green precipitate, soluble in excess | | add aqueous ammonia | no observable change | green precipitate, insoluble in excess | | flame test | lilac flame | not tested | Which row shows the identities of the ions present in P and Q?

1. AP: K⁺ and SO₄²⁻; Q: Cr³⁺ and CO₃²⁻
2. BP: K⁺ and CO₃²⁻; Q: Fe²⁺ and SO₄²⁻
3. CP: K⁺ and CO₃²⁻; Q: Cr³⁺ and SO₄²⁻
4. DP: Li⁺ and CO₃²⁻; Q: Cr³⁺ and SO₄²⁻

As printed in the paper