Hydrogen can be made by reacting methane with steam:
CH4+H2O→CO+3H2\text{CH}_4 + \text{H}_2\text{O} \rightarrow \text{CO} + 3\text{H}_2CH4+H2O→CO+3H2
Each methane molecule contains four C-H\text{C-H}C-H bonds and each water molecule contains two O-H\text{O-H}O-H bonds. Each carbon monoxide molecule contains one C≡O\text{C}\equiv\text{O}C≡O bond, and each hydrogen molecule contains one H-H\text{H-H}H-H bond.
| Bond | Bond energy in kJ/mol |
|---|---|
| C-H\text{C-H}C-H | 413 |
| O-H\text{O-H}O-H | 463 |
| C≡O\text{C}\equiv\text{O}C≡O | 1077 |
| H-H\text{H-H}H-H | 436 |
Calculate how much energy is required to break the bonds in the methane and water molecules.
Calculate how much energy is released as the bonds in carbon monoxide and hydrogen form.
Calculate, from the bond totals in parts (a) and (b), the overall energy change for the reaction of methane with steam.
Explain the direction of energy transfer between the reacting chemicals and their surroundings during this reaction.
85 exam-style questions on AQA GCSE Chemistry 5.1 Exothermic and endothermic reactions, covering 5.1.1 Energy transfer during exothermic and endothermic reactions, 5.1.2 Reaction profiles, and 5.1.3 The energy change of reactions. Each one has a worked solution and a mark scheme showing where the marks go.