International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

Which ion is confirmed by a cream precipitate when tested with silver nitrate?

1. Chloride ion

2. Bromide ion

3. Iodide ion

4. Sulfate ion

The correct answer is: Bromide ion

When testing for halide ions using silver nitrate, the formation of a precipitate is indicative of a specific halide compound. Silver nitrate reacts with halide ions to form a precipitate of silver halide, which can vary in color depending on the ion present. In this case, the formation of a cream precipitate when tested with silver nitrate is characteristic of the bromide ion. The reaction between silver ions (from silver nitrate) and bromide ions results in the formation of silver bromide, which has a cream-colored appearance. This is a definitive test for bromide ions in solution. Chloride ions produce a white precipitate due to silver chloride, while iodide ions yield a yellow precipitate of silver iodide. The sulfate ion does not form a precipitate with silver nitrate, and thus does not match the criteria for a cream precipitate.