A chemist keeps equal samples of a reaction mixture at different temperatures. The mixture changes from colourless to blue.
The chemist records the time taken for each sample to reach the same shade of blue.
| Temperature (∘C^\circ\mathrm{C}∘C) | 15 | 55 |
|---|---|---|
| Time to reach the same shade (s) | 128 | 8 |
Which conclusion is supported by the results?
The rate at 15 ∘C15\,^\circ\mathrm{C}15∘C is 16 times the rate at 55 ∘C55\,^\circ\mathrm{C}55∘C, as the time taken is 16 times as long.
The rate at 55 ∘C55\,^\circ\mathrm{C}55∘C is 120 times the rate at 15 ∘C15\,^\circ\mathrm{C}15∘C, as the time taken is 120 s120\,\mathrm{s}120s less.
The relative rate at 55 ∘C55\,^\circ\mathrm{C}55∘C is 8 s−18\,\mathrm{s}^{-1}8s−1, as the colour change takes 8 s at this temperature.
The rate at 55 ∘C55\,^\circ\mathrm{C}55∘C is 16 times the rate at 15 ∘C15\,^\circ\mathrm{C}15∘C, as the time taken is one-sixteenth as long.
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.