Chlorine can be made by reacting hydrogen chloride gas with oxygen.
4HCl(g)+O2(g)⇌2Cl2(g)+2H2O(g) \mathrm{4HCl(g) + O_{2}(g) \rightleftharpoons 2Cl_{2}(g) + 2H_{2}O(g)} 4HCl(g)+O2(g)⇌2Cl2(g)+2H2O(g)The forward reaction is exothermic.
The table shows the percentage of hydrogen chloride converted to chlorine at equilibrium under different conditions.
| Temperature (°C) | Hydrogen chloride converted at 1 atm (%) | Hydrogen chloride converted at 5 atm (%) |
|---|---|---|
| 250 | 92 | 95 |
| 350 | 84 | 89 |
| 450 | 73 | 80 |
| 550 | 61 | 70 |
Which conditions in the table give the highest percentage of hydrogen chloride converted?
Explain the effects of temperature and pressure shown in the table.
Suggest two other ways to increase the amount of chlorine in the equilibrium mixture, and explain whether adding a catalyst would increase the percentage of hydrogen chloride converted.
The company runs the process at about 400 °C, not 250 °C.
Suggest why.
47 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.