Reactant gases were passed through a heated tube. The same quantity of reactant gas was used in each experiment, at the same temperature and pressure. Each experiment was stopped when 30 cm3 of product gas had been collected.
| Experiment | Time to collect 30 cm3 of product gas in s | Activation energy in kJ/mol\text{kJ/mol}kJ/mol | Mass of X before the reaction in g | Mass of X after the reaction in g |
|---|---|---|---|---|
| Without solid X | 140 | 115 | – | – |
| With solid X | 55 | 68 | 0.60 | 0.60 |
Explain how the results show that X is a catalyst and why the rate changes.
127 exam-style questions on AQA GCSE Chemistry 6.1 Rate of reaction, covering 6.1.1a Calculating rates of reactions, 6.1.1b Gradient of a tangent as rate, 6.1.2 Factors which affect the rates of chemical reactions, 6.1.3 Collision theory and activation energy, and 6.1.4 Catalysts. Each one has a worked solution and a mark scheme showing where the marks go.