A metal-finishing plant recovers two pure solid ionic compounds, P and Q, from separate process streams. Each test is carried out on a separate portion. The tests on P use the solid. The tests on Q use a solution of Q in water.
| Compound | Test | Result |
|---|---|---|
| P | Flame test | Orange-red flame |
| P | Add dilute acid and bubble the gas produced through limewater | Fizzing; the limewater turns milky |
| Q | Add sodium hydroxide solution | Blue precipitate |
| Q | Add dilute hydrochloric acid, then barium chloride solution | White precipitate |
| Q | Add dilute hydrochloric acid, then silver nitrate solution | White precipitate |
Use the first four test results to identify compounds P and Q. Explain your answer.
Evaluate whether the result of the halide test should change the identification of compound Q.
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.