Hydrogen, H2\text{H}_2H2, reacts with iodine, I2\text{I}_2I2, to form hydrogen iodide, HI\text{HI}HI.
H2(g)+I2(g)⇌2HI(g) \text{H}_2\text{(g)} + \text{I}_2\text{(g)} \rightleftharpoons 2\text{HI(g)} H2(g)+I2(g)⇌2HI(g)The reaction takes place in a sealed vessel. The mixture is initially at equilibrium. Some gas is removed and the vessel is immediately sealed again. The temperature and vessel volume remain constant throughout.
| Measurement | Concentration of H2\text{H}_2H2 in mol/dm3\text{mol/dm}^3mol/dm3 | Concentration of I2\text{I}_2I2 in mol/dm3\text{mol/dm}^3mol/dm3 | Concentration of HI\text{HI}HI in mol/dm3\text{mol/dm}^3mol/dm3 |
|---|---|---|---|
| Just before the gas is removed | 0.360 | 0.280 | 0.900 |
| Immediately after the gas is removed | 0.360 | 0.280 | 0.400 |
| At the new equilibrium | 0.257 | 0.177 | 0.605 |
A student makes this statement:
“I2\text{I}_2I2 was removed. The equilibrium then moved to the left to replace the I2\text{I}_2I2.”
Evaluate the student's statement.
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.