A colourless solution reacts with a blue solution. As the reaction takes place, the blue colour fades.
A student records the time taken for the mixture to reach the same shade of blue. The student uses the same volumes of both solutions in each experiment. All other conditions are kept the same.
| Experiment | Concentration of the colourless solution / mol/dm3\mathrm{mol/dm^{3}}mol/dm3 | Temperature / ∘C^\circ\mathrm{C}∘C | Time / s\mathrm{s}s |
|---|---|---|---|
| 1 | 0.80 | 20 | 50 |
| 2 | 0.40 | 20 | 100 |
| 3 | 0.40 | 30 | 50 |
The student carries out experiment 4 using a concentration of 0.20 mol/dm30.20\,\mathrm{mol/dm^{3}}0.20mol/dm3 at 10 ∘C10\,^\circ\mathrm{C}10∘C.
Calculate the expected time for the mixture to reach the same shade of blue. Use the patterns in the results.
Explain, using ideas about particles, why experiment 4 is expected to take longer than experiment 2.
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.