Gases X and Y react in a sealed vessel to form gaseous product XY₂.
X(g)+2Y(g)→XY2(g)\mathrm{X(g) + 2Y(g) \rightarrow XY_2(g)}X(g)+2Y(g)→XY2(g)
Five experiments use the same initial amounts of X and Y. In every experiment, a maximum of 0.0400 mol of XY₂ can form. A detector records the amount of XY₂ present after 40 s. None of the reactions is complete after 40 s.
| Experiment | Temperature in K | Pressure in kPa | Catalyst added | Amount of XY₂ after 40 s in mol |
|---|---|---|---|---|
| A | 300 | 100 | no | 0.0060 |
| B | 300 | 200 | no | 0.0118 |
| C | 330 | 100 | no | 0.0130 |
| D | 330 | 200 | no | 0.0250 |
| E | 300 | 100 | yes | 0.0240 |
Calculate the mean rate of formation of XY₂ in experiment D, in mol/s\mathrm{mol/s}mol/s, and determine how many times greater this is than the mean rate in experiment A.
A student says, "Doubling the pressure has exactly the same effect on the rate as increasing the temperature from 300 K to 330 K because both changes only put the particles closer together."
Evaluate this statement. Use collision theory and the data in your answer.
Explain why the catalyst in experiment E changes the amount of XY₂ formed after 40 s but does not change the final amount formed.
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.