Ammonia is made by reacting nitrogen with hydrogen. A technician tests whether iron powder acts as a catalyst. The same initial amounts of nitrogen and hydrogen are used in both experiments. Apart from the addition of iron, both experiments are carried out under identical conditions.
| Experiment | Iron added / g | Time to form 1.50 g of ammonia / s | Final mass of ammonia / g | Iron recovered / g |
|---|---|---|---|---|
| 1 | 0.00 | 310 | 2.40 | not applicable |
| 2 | 1.00 | 125 | 2.40 | 1.00 |
Calculate the mean rate at which ammonia forms during the first 125 s of experiment 2. Give the unit.
Explain how the results support the conclusion that iron is a catalyst for this reaction.
Explain, in terms of activation energy and collisions, why adding iron increases the rate of this reaction.
State two conditions, other than the initial amounts of nitrogen and hydrogen, that were kept the same in both experiments.
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.