A quality-control technician at a gas supplier checks a cylinder labelled 'oxygen'. A glowing splint held in the laboratory air keeps glowing but does not relight. When the same glowing splint is lowered into a test tube of gas from the cylinder, it relights.
Why does the splint relight in the gas from the cylinder but not in the laboratory air?
The gas is warmer than the air, so it heats the splint until it ignites.
The air contains carbon dioxide, which stops the splint from relighting.
The gas from the cylinder is flammable, but the air is not.
The gas has a much higher proportion of oxygen than the air has.
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.