A student carries out the core practical to identify the ions in three unknown salts, P, Q and R. She dissolves each salt in distilled water and carries out two tests on each solution.
The table shows her results.
| Salt | Test 1 | Result of test 1 | Test 2 | Result of test 2 |
|---|---|---|---|---|
| P | flame test | yellow flame | add dilute nitric acid, then silver nitrate solution | cream precipitate |
| Q | add sodium hydroxide solution | blue precipitate | add dilute hydrochloric acid, then barium chloride solution | white precipitate |
| R | add sodium hydroxide solution and warm | gas turns damp red litmus paper blue | add dilute nitric acid, then silver nitrate solution | white precipitate |
Name salts P, Q and R.
Sulfate ions are SO42−\mathrm{SO_{4}^{2-}}SO42−. Use your answer to (a) to give the formula of salt Q.
The student uses a fresh sample of each solution for each test. Explain why.
Sodium hydroxide solution is corrosive. Give one safety precaution the student should take when using it.
The student carries out a flame test on salt Q. Predict the colour of the flame.
35 exam-style questions on Edexcel GCSE Chemistry 10.1 Qualitative analysis: tests for ions, covering 10.1.1 Principles of ion tests and flame tests, 10.1.2 Tests for cations and for ammonia, 10.1.3 Tests for anions, 10.1.4 Identification of ions in unknown salts, and 10.1.5 Instrumental methods of analysis. Each one has a worked solution and a mark scheme showing where the marks go.