All calculations
Concentration in mol/dm3
Quantitative chemistry
AQA 8462
ORIGINAL
Higher tier
c = n / V; n = m / Mr
Convert mass to moles first, then divide by the solution volume in dm3.
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
3 marks
4.0 g of NaOH is dissolved to make 500 cm3 of solution. Calculate the concentration in mol/dm3. (Mr(NaOH) = 40)
Do the calculation on paper first — then mark it.
Where the marks get lost
- Dividing the mass directly by volume without converting to moles.
- Forgetting that 500 cm3 is 0.500 dm3.
Exam tip: Write two equations on separate lines: n = m/Mr, then c = n/V.
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.