Two colourless solutions react to form a coloured product. A student records the time taken for the mixture to reach the same fixed colour standard in each experiment.
The relative rate of each reaction is given by:
relative rate=1time \text{relative rate} = \frac{1}{\text{time}} relative rate=time1The student uses equal volumes of the reactant solutions. Except for the conditions shown in the table, all conditions and quantities are the same. The catalyst used in experiment D is suitable for this reaction.
| Experiment | Concentration of one reactant solution in g/dm3\mathrm{g/dm^3}g/dm3 | Temperature in ∘C^\circ\mathrm{C}∘C | Catalyst | Time to reach the fixed colour standard in s\mathrm{s}s |
|---|---|---|---|---|
| A | 4.0 | 20 | absent | 96 |
| B | 8.0 | 20 | absent | 52 |
| C | 4.0 | 30 | absent | 38 |
| D | 4.0 | 20 | present | 31 |
Calculate how many times greater the relative rate is in experiment D than in experiment A.
Compare the effects on the rate of doubling the concentration in experiment B and raising the temperature in experiment C. Use the results and collision theory in your answer.
A student concludes, "The catalyst makes the reacting particles move faster, so experiment D will form more coloured product in total once both reactions have finished than experiment A."
Evaluate this conclusion.
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.