A coloured substance is used up during a reaction. The colour reading of the mixture is measured at intervals.
| Time in s | Colour reading in arbitrary units |
|---|---|
| 0 | 120 |
| 10 | 90 |
| 20 | 68 |
| 35 | 40 |
| 50 | 24 |
What is the mean rate, based on the change in colour reading, from 10 s to 35 s?
1.6 arbitrary units s−11.6\,\mathrm{arbitrary\ units\,s^{-1}}1.6arbitrary unitss−1
2.0 arbitrary units s−12.0\,\mathrm{arbitrary\ units\,s^{-1}}2.0arbitrary unitss−1
3.6 arbitrary units s−13.6\,\mathrm{arbitrary\ units\,s^{-1}}3.6arbitrary unitss−1
1.4 arbitrary units s−11.4\,\mathrm{arbitrary\ units\,s^{-1}}1.4arbitrary unitss−1
122 exam-style questions on Edexcel GCSE Chemistry 8.1 Rates of reaction, covering 8.1.1 Measuring and interpreting rates of reaction, 8.1.2 Collision theory and the factors affecting rate, and 8.1.3 Catalysts and enzymes. Each one has a worked solution and a mark scheme showing where the marks go.