A sealed reaction vessel initially contains both substance M and substance N. Substance M changes reversibly into substance N. The change from M to N is the forward reaction.
A sensor records the rates of the forward and reverse reactions under constant conditions.
| Time (s) | Rate of forward reaction (arbitrary units) | Rate of reverse reaction (arbitrary units) |
|---|---|---|
| 0 | 1.2 | 7.8 |
| 20 | 2.8 | 5.4 |
| 40 | 3.8 | 4.3 |
| 60 | 4.0 | 4.0 |
Which statement is correct?
At 0 s, substance N is being made overall.
At 60 s, there is still an overall change from substance N to substance M.
At 40 s, the forward reaction is faster than the reverse reaction.
At 20 s, the overall change is from substance N to substance M.
124 exam-style questions on OCR GCSE Chemistry 5.3 Equilibria, covering 5.3.1 Reversible reactions and dynamic equilibrium and 5.3.2 Changing the position of equilibrium. Each one has a worked solution and a mark scheme showing where the marks go.