A technician exposes two strips of blue litmus paper to the same unknown gas.
| Time after exposure in seconds | Damp blue litmus paper | Dry blue litmus paper |
|---|---|---|
| 0 | blue | blue |
| 5 | red | blue |
| 30 | white | blue |
Explain how the observations identify the gas and why the dry litmus paper does not change.
89 exam-style questions on AQA GCSE Chemistry 8.2 Identification of common gases, covering 8.2.1 Test for hydrogen, 8.2.2 Test for oxygen, 8.2.3 Test for carbon dioxide, and 8.2.4 Test for chlorine. Each one has a worked solution and a mark scheme showing where the marks go.