Copper is 69.2% Cu-63 and 30.8% Cu-65. Calculate its relative atomic mass.
[2 marks]
Total for this question: 2
All calculations
Relative atomic mass from isotopes
Atomic structure
AQA 8462
ORIGINAL
Ar = sum(isotope mass x abundance) / sum(abundances)
The abundances are weights: multiply first, add, then divide by the total abundance.
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
- Taking an unweighted mean of the isotope masses.
- Using percentage abundances but forgetting to divide by 100.
Exam tip: Your answer must lie between the isotope masses and be nearer the more abundant isotope.
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