A student adds a 2 cm piece of magnesium ribbon to dilute hydrochloric acid at different temperatures. The student times how long it takes for the magnesium to disappear.
| Temperature (∘C^\circ\mathrm{C}∘C) | 20 | 30 | 40 | 50 |
|---|---|---|---|---|
| Time for magnesium to disappear (s) | 120 | 62 | 31 | 16 |
Which conclusion is supported by the results?
Each 10 ∘C10\,^\circ\mathrm{C}10∘C rise roughly doubles the time, so the rate halves.
The rate at 50 ∘C50\,^\circ\mathrm{C}50∘C is about 4 times the rate at 20 ∘C20\,^\circ\mathrm{C}20∘C.
Each 10 ∘C10\,^\circ\mathrm{C}10∘C rise roughly halves the time, so the rate doubles.
The time taken is directly proportional to the temperature.
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.