Two dissolved substances react reversibly in a sealed container at constant temperature.
P(aq)⇌Q(aq) \mathrm{P(aq) \rightleftharpoons Q(aq)} P(aq)⇌Q(aq)The concentrations of P and Q are measured at intervals.
| Time (min) | Concentration of P (mol/dm³) | Concentration of Q (mol/dm³) |
|---|---|---|
| 0 | 0.68 | 0.12 |
| 2 | 0.56 | 0.24 |
| 4 | 0.49 | 0.31 |
| 6 | 0.45 | 0.35 |
| 8 | 0.44 | 0.36 |
| 10 | 0.44 | 0.36 |
Which conclusion is supported by the results?
Dynamic equilibrium was reached after 4 minutes but no later than 6 minutes, and at 6 minutes the forward and reverse reactions were happening at the same rate.
Dynamic equilibrium was reached after 6 minutes but no later than 8 minutes, and at 10 minutes the forward and reverse reactions were happening at the same rate.
Dynamic equilibrium was reached after 8 minutes but no later than 10 minutes, and at 8 minutes the forward reaction was faster than the reverse reaction.
Dynamic equilibrium had not been reached by 10 minutes, and at 10 minutes the reverse reaction was faster than the forward reaction.
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.