The steam reforming of methane to produce synthesis gas is an important industrial process represented by the following chemical equation:
CH4(g)+H2O(g)⟶CO(g)+3H2(g)ΔH⊖=+206 kJ mol−1 \text{CH}_4(\text{g}) + \text{H}_2\text{O}(\text{g}) \longrightarrow \text{CO}(\text{g}) + 3\text{H}_2(\text{g}) \quad \Delta H^{\ominus} = +206 \text{ kJ mol}^{-1} CH4(g)+H2O(g)⟶CO(g)+3H2(g)ΔH⊖=+206 kJ mol−1Some standard entropy data are shown in the table below:
| Substance | CH4(g)\text{CH}_4(\text{g})CH4(g) | H2O(g)\text{H}_2\text{O}(\text{g})H2O(g) | CO(g)\text{CO}(\text{g})CO(g) | H2(g)\text{H}_2(\text{g})H2(g) |
|---|---|---|---|---|
| S⊖ / J K−1mol−1S^{\ominus} \text{ / J K}^{-1}\text{mol}^{-1}S⊖ / J K−1mol−1 | 186186186 | 189189189 | 198198198 | 131131131 |
Use the equation and the entropy data to calculate the Gibbs free-energy change (ΔG\Delta GΔG) for this reaction at 750 ∘C750\,^{\circ}\text{C}750∘C. Give your answer to an appropriate number of significant figures.
Use your answer to explain whether this reaction is feasible at this temperature.
27 exam-style questions on AQA A Level Chemistry Thermodynamics (A-level only), covering Born–Haber cycles (A-level only) and Gibbs free-energy change, $\Delta G$ , and entropy change, $\Delta S$ (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.