A mixture of gases reaches equilibrium in a sealed vessel at constant temperature.
A(g)+2B(g)⇌D(g) \mathrm{A(g) + 2B(g) \rightleftharpoons D(g)} A(g)+2B(g)⇌D(g)At 5.0 minutes, one of the gases is injected into the vessel.
| Time | Concentration of A / mol dm−3\text{mol dm}^{-3}mol dm−3 | Concentration of B / mol dm−3\text{mol dm}^{-3}mol dm−3 | Concentration of D / mol dm−3\text{mol dm}^{-3}mol dm−3 |
|---|---|---|---|
| Just before 5.0 minutes | 0.50 | 0.60 | 0.20 |
| Immediately after 5.0 minutes | 0.50 | 0.90 | 0.20 |
| At the new equilibrium | 0.43 | 0.76 | 0.27 |
Describe the change made at 5.0 minutes and how the equilibrium mixture responds. Use the data to show whether the response increases or reduces the effect of the change.
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.