Calculate the relative formula mass, Mr, of Al2(SO4)3. (Ar: Al = 27, S = 32, O = 16)
[2 marks]
Total for this question: 2
All calculations
Relative formula mass
Quantitative chemistry
AQA 8462
ORIGINAL
Mr = sum of every Ar in the formula
One missed subscript changes every later answer, so expand the formula before adding.
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
- Counting only four oxygen atoms instead of twelve.
- Adding the small formula numbers instead of multiplying each Ar.
Exam tip: Write the number of each atom underneath the formula before using the periodic table.
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