A solution contains either calcium iodide or zinc iodide.
A student adds sodium hydroxide solution to a sample of the solution. A white precipitate forms.
Which further test would show which compound is in the solution?
Add dilute nitric acid, then silver nitrate solution. Calcium iodide gives a yellow precipitate, but zinc iodide gives a cream precipitate.
Do a flame test. Calcium ions give an orange-red flame, but zinc ions do not.
Add dilute hydrochloric acid, then barium chloride solution. Calcium iodide gives a white precipitate, but zinc iodide does not.
Add more sodium hydroxide solution. Calcium ions give a blue precipitate, but zinc ions give a white precipitate.
107 exam-style questions on OCR GCSE Chemistry 4.2 Identifying the products of chemical reactions, covering 4.2.1 Tests to identify gases, 4.2.2 Tests for aqueous ions and flame tests, and 4.2.3 Instrumental methods of analysis. Each one has a worked solution and a mark scheme showing where the marks go.