2H2 + O2 → 2H2O. A mixture contains 3.0 mol H2 and 2.0 mol O2. Identify the limiting reactant and calculate the moles of water formed.
[3 marks]
Total for this question: 3
All calculations
Limiting reactant
Quantitative chemistry
AQA 8462
ORIGINAL
Higher tier
compare moles / balancing coefficient for each reactant
The smaller mass is not automatically limiting; compare available moles with the equation ratio.
Board and spec code confirmed against AQA 8462 · registry checked 2026-07-17How this checking works
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
Do the calculation on paper first — then mark it.
Where the marks get lost
- Choosing the reactant with fewer moles without using coefficients.
- Using all of the excess reactant to calculate product.
Exam tip: Divide each mole amount by its balancing number; the smallest result identifies the limiter.
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