Human gas exchange: past paper questions
Real questions on human gas exchange
The newest 6 of 6 written questions, plus 23 multiple-choice. Open one to see it on the real paper.
- 5129/21 · October/November 2025 · Q2a[1]
State the percentage of nitrogen gas, N 2 , in clean, dry air. %
See it on the paper → - 5129/21 · October/November 2025 · Q4a[2]
Inspired air is air that is breathed in, and expired air is air that is breathed out. Complete the sentences comparing inspired and expired air. Inspired air has more than expired air.
See it on the paper → - 5129/21 · October/November 2025 · Q4b(i)[1]
Use the graph to determine the student’s breathing rate when the student is standing still before exercising. breaths / min
See it on the paper → - 5129/31 · October/November 2023 · Q1b(iii)[2]
In another investigation, the student uses the test for carbon dioxide to show that the amount of carbon dioxide in exhaled air is greater than the amount of carbon dioxide in atmospheric air. The student collects a sample of exhaled air from friend A and a sample of atmospheric air and then bubbles each sample through...
See it on the paper → - 5129/31 · October/November 2023 · Q1b(iv)[1]
The student repeats the test for carbon dioxide using a sample of exhaled air from student B. State how this improves the investigation.
See it on the paper → - 5129/22 · May/June 2019 · Q9a[3]
Describe three ways in which expired air is different to inspired air.
See it on the paper →
What examiners said
Candidates were asked to describe the colour of limewater which had exhaled air bubbled through it, and the colour of limewater which had atmospheric air bubbled through it. Many knew that the exhaled air contained more carbon dioxide and that this would turn the limewater milky. However, only a few candidates knew that the small concentration of carbon dioxide in atmospheric air would have no eff...
— Examiner report, October/November 2023, 5129/31 Q1(b)(iii) (Cambridge)
Stronger candidates were able to describe how to improve the investigation. Some candidates used vague terminology that could not be credited.
— Examiner report, October/November 2023, 5129/31 Q1(b)(iv) (Cambridge)
The differences between expired and inspired air were well known by many of the candidates.
— Examiner report, May/June 2019, 5129/22 Q9(a) (Cambridge)
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