A manufacturer investigates the effect of substance C on a reaction. Each experiment starts with the same amounts of the same reactants and is kept at the same temperature. In experiment 3, substance C recovered from experiment 2 is added to a fresh mixture of the reactants.
| Experiment | Substance C added | Time for reaction to finish / s | Products identified | Mass of substance C recovered / g |
|---|---|---|---|---|
| 1 | none | 240 | X and Y | not applicable |
| 2 | 0.50 g of fresh C | 64 | X and Y | 0.50 |
| 3 | 0.50 g of recovered C | 66 | X and Y | 0.50 |
Explain how the results support the conclusion that substance C is a catalyst and does not change the products.
Explain why substance C increases the rate of the reaction.
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.