Solutions A and B react together slowly. A chemist repeats the reaction at the same temperature with a small amount of solid X added. The reaction is faster with solid X.
| Solid added | Activation energy (kJ/mol\mathrm{kJ/mol}kJ/mol) |
|---|---|
| none | 118 |
| X | 74 |
Which statement explains why the reaction is faster with solid X?
Solid X gives the particles 74 kJ/mol74\,\mathrm{kJ/mol}74kJ/mol of extra energy, so more collisions succeed each second.
Solid X makes the particles move faster, so they collide more often with the same energy as before.
Solid X lowers the energy of the products, so more energy is released and the reaction speeds up.
More collisions have at least 74 kJ/mol74\,\mathrm{kJ/mol}74kJ/mol than at least 118 kJ/mol118\,\mathrm{kJ/mol}118kJ/mol, so more succeed each second.
122 exam-style questions on OCR GCSE Chemistry 5.2 Controlling reactions, covering 5.2.1 Measuring and interpreting rate of reaction, 5.2.2 Factors affecting rate and collision theory, and 5.2.3 Catalysts, activation energy and enzymes. Each one has a worked solution and a mark scheme showing where the marks go.