Hydrogen peroxide decomposes to make water and oxygen. The table shows the activation energy for this reaction with different catalysts.
| Catalyst | Activation energy (kJ/mol\mathrm{kJ/mol}kJ/mol) |
|---|---|
| none | 75 |
| iodide ions | 56 |
| catalase (an enzyme found in liver) | 23 |
All the experiments are done at the same temperature.
Which statement is correct?
Catalase lowers the activation energy the most, but it is used up because it is an enzyme.
Catalase gives the greatest rate because the greatest proportion of collisions is successful.
Iodide ions give the greatest rate because they lower the activation energy by 56 kJ/mol56\,\mathrm{kJ/mol}56kJ/mol.
All three give the same rate because the overall energy change is the same.
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.