A tangent to a mass-loss curve passes through (40 s, 1.6 g) and (100 s, 0.7 g). Calculate the magnitude of the rate of mass loss.
[3 marks]
Total for this question: 3
All calculations
Rate from a graph tangent
Rates of reaction
AQA 8462
ORIGINAL
Higher tier
rate at a time = gradient of tangent = change in y / change in x
An instantaneous rate is the gradient of a tangent, not the gradient between arbitrary curve points.
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
- Using points on the curve instead of points on the tangent.
- Forgetting to use differences in both coordinates.
Exam tip: Choose two well-separated, easy-to-read points on the tangent line to reduce reading uncertainty.
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. Free intro call, then a free first lesson.
Stuck on tangent rate?
Everything here stays free. If tangent rate is where the marks keep going, I teach it one to one from the mark schemes. Free intro call, then a free first lesson.