Hydrogen for the Haber process is made by reacting methane with steam.
CH4(g)+H2O(g)⇌CO(g)+3H2(g)\mathrm{CH_{4}(g)} + \mathrm{H_{2}O(g)} \rightleftharpoons \mathrm{CO(g)} + \mathrm{3H_{2}(g)}CH4(g)+H2O(g)⇌CO(g)+3H2(g)
The table shows the percentage of methane converted at equilibrium under different conditions.
| Temperature / °C | Methane converted at 1 atm (%) | Methane converted at 30 atm (%) |
|---|---|---|
| 600 | 72 | 30 |
| 800 | 97 | 65 |
| 1000 | 99 | 88 |
Use the table to describe the effect of increasing the pressure on the percentage of methane converted. Explain this effect using the equation.
Explain what the data show about the energy change of the forward reaction.
A reactor at 800 °C and 30 atm is fed with 1200 dm3\mathrm{dm^{3}}dm3 of methane. Calculate the volume of hydrogen formed at equilibrium. Assume all volumes are measured at the same temperature and pressure.
Industry uses a pressure of 30 atm even though a lower pressure gives a higher percentage conversion. Suggest two reasons why.
The carbon monoxide formed is reacted with more steam to make more hydrogen.
CO(g)+H2O(g)⇌CO2(g)+H2(g)\mathrm{CO(g)} + \mathrm{H_{2}O(g)} \rightleftharpoons \mathrm{CO_{2}(g)} + \mathrm{H_{2}(g)}CO(g)+H2O(g)⇌CO2(g)+H2(g)
The forward reaction is exothermic. Explain why changing the pressure has no effect on the equilibrium yield of hydrogen in this reaction, and why this step is carried out at a lower temperature (about 400 °C) than the first step.
45 exam-style questions on Edexcel GCSE Chemistry 5.2 Reversible reactions and equilibria, covering 5.2.1 Reversible reactions and dynamic equilibrium, 5.2.2 The Haber process, and 5.2.3 Changing the position of a dynamic equilibrium. Each one has a worked solution and a mark scheme showing where the marks go.