AQA GCSE Chemistry
AQA GCSE Chemistry 4.3.5 Moles and Volumes of Gases Exam Questions
Free AQA GCSE Chemistry exam questions for 4.3.5 Moles and Volumes of Gases, with a mark scheme for every pack. Covers the molar gas volume of 24 dm3 at room temperature and pressure, gas volume calculations and volume ratios from equations.
4.3.5 Moles and Volumes of Gases exam questions
1 question pack of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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About AQA GCSE Chemistry 4.3.5 Moles and Volumes of Gases
AQA GCSE Chemistry 4.3.5 is separate Chemistry, Higher tier only content. It shows that equal amounts in moles of any gas occupy the same volume at the same temperature and pressure: 24 dm3 per mole at room temperature and pressure (20 °C and 1 atmosphere). You use this to calculate volumes from masses and moles, and to work out gas volumes from balanced equations. It is assessed on Paper 1 and extends the mole calculations from 4.3.2. Typical questions are short multi-step calculations, often requiring conversion between dm3 and cm3.
What you need to know
- Molar volume (Higher tier only) One mole of any gas occupies 24 dm3 (24 000 cm3) at room temperature and pressure (RTP: 20 °C and 1 atmosphere pressure).
- Volume and moles (Higher tier only) volume of gas (dm3) = moles x 24. moles = volume (dm3) / 24, or volume (cm3) / 24 000.
- From mass to volume (Higher tier only) Convert mass to moles using moles = mass / Mr, then multiply by 24 to find the volume in dm3.
- Volume ratios (Higher tier only) For reacting gases, volumes are in the same ratio as the moles in the balanced equation. For example, in 2H2 + O2 → 2H2O, 50 cm3 of hydrogen reacts with 25 cm3 of oxygen.
- Using equations (Higher tier only) Use the mole ratio to find the moles of gaseous product from a known mass of reactant, then convert to volume.
Common mistakes in 4.3.5 Moles and Volumes of Gases
- Using 24 when the volume is in cm3. Use 24 000 cm3 per mole, or convert to dm3 first.
- Applying molar volume to solids or liquids. It only applies to gases.
- Forgetting the mole ratio: in 2H2 + O2, the volume of hydrogen is twice the volume of oxygen.
- Using 24 dm3 at conditions other than room temperature and pressure without checking the question.
Try three 4.3.5 Moles and Volumes of Gases exam-style questions
1. Calculate the volume of 8.8 g of carbon dioxide at room temperature and pressure. (Mr CO2 = 44) (2 marks)
Show the mark scheme answer
Moles = 8.8 / 44 = 0.20 mol; volume = 0.20 x 24 = 4.8 dm3.
2. What volume of oxygen is needed to react completely with 60 cm3 of hydrogen? 2H2 + O2 → 2H2O (1 mark)
Show the mark scheme answer
30 cm3.
3. Calculate the number of moles in 600 cm3 of nitrogen gas at room temperature and pressure. (2 marks)
Show the mark scheme answer
600 cm3 = 0.600 dm3 (or use 24 000 cm3); moles = 0.600 / 24 = 0.025 mol.
4.3.5 Moles and Volumes of Gases FAQs
What does AQA GCSE Chemistry 4.3.5 cover?
It covers the molar gas volume of 24 dm3 at room temperature and pressure, converting between moles, masses and gas volumes, and using balanced equations to find volumes of gaseous reactants and products.
Who needs to learn 4.3.5?
It is separate Chemistry content and is Higher tier only, assessed on Paper 1.
What should I memorise for gas volume questions?
Learn that 1 mol of gas occupies 24 dm3 (24 000 cm3) at RTP, and the equation volume = moles x 24. Always check the units the question uses.
