25.0 cm3 of 0.100 mol/dm3 H2SO4 neutralises 20.0 cm3 of NaOH. H2SO4 + 2NaOH → Na2SO4 + 2H2O. Calculate the NaOH concentration.
[4 marks]
Total for this question: 4
All calculations
A-level titration stoichiometry
Amount of substance
AQA 7405
ORIGINAL
n = cV; use equation ratio; c = n/V
The aliquot volumes belong to different chemicals; attach each volume to its concentration before using the ratio.
Board and spec code confirmed against AQA 7405 · registry checked 2026-07-11How 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
- Using a 1:1 ratio for a diprotic acid.
- Dividing by 20.0 instead of 0.0200 dm3.
Exam tip: Write the known chemical's n = cV line first and annotate the balanced equation with the resulting mole ratio.
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