A student investigates the effect of temperature on a reaction. A purple reactant is used up as the reaction proceeds, causing the mixture to fade. The volumes and concentrations of the reactants are the same in every experiment.
The table shows the student's first measurements.
| Temperature in ∘C^\circ\mathrm{C}∘C | Endpoint used | Time in s |
|---|---|---|
| 20 | mixture becomes pale purple | 36 |
| 30 | mixture becomes colourless | 48 |
The student concludes that the reaction is faster at 20 ∘C20\,^\circ\mathrm{C}20∘C because 1/36 1/36\,1/36 is greater than 1/481/481/48.
Explain whether this conclusion is valid.
The student carries out three experiments at each temperature, recording the time taken for the mixture to become colourless.
| Temperature in ∘C^\circ\mathrm{C}∘C | Time in experiment 1 in s | Time in experiment 2 in s | Time in experiment 3 in s |
|---|---|---|---|
| 20 | 74 | 71 | 71 |
| 30 | 47 | 49 | 48 |
For these results, the relative rate is calculated using 1/mean time1/\text{mean time}1/mean time.
Calculate the ratio of the relative rate at 30 ∘C30\,^\circ\mathrm{C}30∘C to the relative rate at 20 ∘C20\,^\circ\mathrm{C}20∘C.
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.