All calculations
Reacting gas volumes
Quantitative chemistry
AQA 8462
ORIGINAL
Higher tier
gas volume ratio = balancing coefficient ratio
At the same temperature and pressure, gas volumes follow the balanced equation's mole ratio.
Verified against AQA 8462 (2026 spec)
Work it, then mark it
Do each calculation on paper first, then reveal the mark scheme and tick the marks you actually earned — the same way you should mark past papers.
Q1
2 marks
N2(g) + 3H2(g) → 2NH3(g). What volume of ammonia forms from 45 cm3 of hydrogen when nitrogen is in excess, at the same conditions?
Do the calculation on paper first — then mark it.
Where the marks get lost
- Using formula subscripts instead of equation coefficients.
- Applying a gas-volume ratio to a solid or liquid reactant.
Exam tip: This shortcut works only for gases compared at the same temperature and pressure.
Calculations are the most trainable marks in chemistry
They come up every paper and reward a clean method. Send me one you keep dropping marks on — your first lesson is free.