All calculations
Percentage yield
Quantitative chemistry
AQA 8462
ORIGINAL
percentage yield = (actual yield / theoretical yield) x 100
Actual over theoretical — and a yield above 100% always means an arithmetic slip.
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
2 marks
A student made 6.0 g of product in a reaction that should theoretically produce 8.0 g. Calculate the percentage yield.
Do the calculation on paper first — then mark it.
Where the marks get lost
- Dividing the theoretical yield by the actual yield (it's actual on top).
- Getting a yield above 100% — impossible, so re-check the arithmetic.
- Confusing percentage yield (about the experiment) with atom economy (about the equation).
Exam tip: Actual yield goes on top. If the numbers give more than 100%, you've flipped the fraction — swap them.
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.