Reactant X in a solution reacts with reactant Y. Y is in large excess, so its concentration remains nearly constant. The volume and temperature of the reaction mixture remain constant.
The table shows the mass of X remaining at different times.
| Time in s | Mass of X remaining in g |
|---|---|
| 0 | 5.00 |
| 20 | 3.20 |
| 40 | 2.10 |
| 60 | 1.40 |
Calculate the mean rate at which X is used up:
Give both rates in g/s\mathrm{g/s}g/s.
Explain why the mean rate is lower from 40 to 60 s than from 0 to 20 s.
122 exam-style questions on OCR GCSE Chemistry 5.2 Controlling reactions, covering 5.2.1 Measuring and interpreting rate of reaction, 5.2.2 Factors affecting rate and collision theory, and 5.2.3 Catalysts, activation energy and enzymes. Each one has a worked solution and a mark scheme showing where the marks go.