Water is converted into hydrogen and oxygen.
2H2O→2H2+O2 2\mathrm{H_2O \rightarrow 2H_2 + O_2} 2H2O→2H2+O2The table shows some bond energies.
| Bond | O−H\mathrm{O{-}H}O−H | H−H\mathrm{H{-}H}H−H | O=O\mathrm{O{=}O}O=O |
|---|---|---|---|
| Bond energy (kJ/mol\mathrm{kJ/mol}kJ/mol) | 463 | 436 | 498 |
What is the energy change, in kJ/mol\mathrm{kJ/mol}kJ/mol, for the equation as written?
+482 kJ/mol+482\,\mathrm{kJ/mol}+482kJ/mol
+1852 kJ/mol+1852\,\mathrm{kJ/mol}+1852kJ/mol
−482 kJ/mol-482\,\mathrm{kJ/mol}−482kJ/mol
+3222 kJ/mol+3222\,\mathrm{kJ/mol}+3222kJ/mol
106 exam-style questions on OCR GCSE Chemistry 3.2 Energetics, covering 3.2.1 Exothermic and endothermic reactions and reaction profiles and 3.2.2 Calculating energy change from bond energies. Each one has a worked solution and a mark scheme showing where the marks go.