Methane burns completely in oxygen: CH4+2O2\text{CH}_4 + 2\text{O}_2CH4+2O2 goes to CO2+2H2O\text{CO}_2 + 2\text{H}_2\text{O}CO2+2H2O. The table gives the bond energies.
Table: The bond energies of the bonds in the reactants and in the products
| Bond | Bond energy in kJ/mol |
|---|---|
| C-H\text{C-H}C-H | 413 |
| O=O\text{O=O}O=O | 498 |
| C=O\text{C=O}C=O | 805 |
| O-H\text{O-H}O-H | 464 |
What is the overall energy change of the reaction?
−1316 kJ/mol-1316\ \text{kJ/mol}−1316 kJ/mol
+818 kJ/mol+818\ \text{kJ/mol}+818 kJ/mol
−818 kJ/mol-818\ \text{kJ/mol}−818 kJ/mol
−6114 kJ/mol-6114\ \text{kJ/mol}−6114 kJ/mol
39 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.