Chemistry · May / June 2025 · Paper 12 · Question 40

A sample of a white powder, X, is dissolved in water. Tests are done on separate portions of this solution and the observations are shown in the table. test | observation add aqueous sodium hydroxide a drop at a time until in excess | white precipitate forms, soluble in excess, giving a colourless solution acidify with dilute nitric acid then add aqueous silver nitrate | white precipitate forms acidify with dilute nitric acid then add aqueous barium nitrate | the solution remains colourless What is X?

1. Aaluminium chloride
2. Baluminium sulfate
3. Ccalcium chloride
4. Dcalcium sulfate

As printed in the paper