A chemist investigates whether solid C catalyses two different reactions, P and Q.
For each reaction, all conditions are kept the same apart from whether solid C is added. The time taken to form a fixed amount of product is measured.
| Reaction | Solid C | Energy of reactants in kJ/mol\mathrm{kJ/mol}kJ/mol | Energy at peak in kJ/mol\mathrm{kJ/mol}kJ/mol | Time in s\mathrm{s}s |
|---|---|---|---|---|
| P | absent | 70 | 230 | 125 |
| P | present | 70 | 170 | 50 |
| Q | absent | 85 | 205 | 80 |
| Q | present | 85 | 205 | 80 |
In each test with solid C, its mass is 0.50 g before the reaction and 0.50 g after it has been recovered.
A student claims that solid C is a catalyst for both reactions.
Evaluate the student's claim.
Use calculations and the information given in your answer.
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.