The table gives energy values from the reaction profiles of four different reactions, P, Q, R and S.
| Reaction | Energy of reactants (kJ/mol\mathrm{kJ/mol}kJ/mol) | Energy at peak (kJ/mol\mathrm{kJ/mol}kJ/mol) | Energy of products (kJ/mol\mathrm{kJ/mol}kJ/mol) |
|---|---|---|---|
| P | 100 | 180 | 40 |
| Q | 20 | 120 | 90 |
| R | 150 | 200 | 60 |
| S | 200 | 260 | 30 |
All four reactions are done at the same temperature, and the particles collide equally often in each reaction.
Which reaction is likely to be the fastest?
Reaction P
Reaction Q
Reaction R
Reaction S
56 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.