A mixture of A, B, C and D is at equilibrium in a closed vessel.
A(aq)+B(aq)⇌C(aq)+D(aq) \text{A(aq)} + \text{B(aq)} \rightleftharpoons \text{C(aq)} + \text{D(aq)} A(aq)+B(aq)⇌C(aq)+D(aq)A technician removes a fixed portion of one substance and closes the vessel again. The mixture is allowed to reach a new equilibrium. The table shows the concentrations before the removal and immediately afterwards.
| Substance | Concentration before removal (mol/dm³) | Concentration immediately after removal (mol/dm³) |
|---|---|---|
| A | 0.40 | 0.40 |
| B | 0.30 | 0.30 |
| C | 0.20 | 0.20 |
| D | 0.50 | 0.35 |
Use the table to identify which substance was removed. Explain how the equilibrium changes and predict what happens to the concentration of C as the mixture reaches the new equilibrium.
109 exam-style questions on AQA GCSE Chemistry 6.2 Reversible reactions and dynamic equilibrium, covering 6.2.1 Reversible reactions, 6.2.2 Energy changes and reversible reactions, 6.2.3 Equilibrium, 6.2.4 The effect of changing conditions on equilibrium, 6.2.5 The effect of changing concentration, 6.2.6 The effect of temperature changes on equilibrium, and 6.2.7 The effect of pressure changes on equilibrium. Each one has a worked solution and a mark scheme showing where the marks go.