A student shakes a test tube of gas with limewater and the limewater turns milky. The student then puts a glowing splint into a second tube of the same gas and the splint does not relight. The student concludes that the gas is a mixture of carbon dioxide and oxygen. Which judgement of this conclusion is correct?
Correct, because carbon dioxide and oxygen were both tested for.
Correct, because a glowing splint only ever detects oxygen gas.
Incorrect, because limewater turning milky rules out oxygen gas.
Incorrect, because the splint result gives no evidence for oxygen.
40 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.