Hydrogen peroxide decomposes to make water and oxygen.
2H2O2→2H2O+O2 \mathrm{2H_{2}O_{2} \rightarrow 2H_{2}O + O_{2}} 2H2O2→2H2O+O2The displayed formula of hydrogen peroxide is H−O−O−H\mathrm{H{-}O{-}O{-}H}H−O−O−H.
| Bond | O−H\mathrm{O{-}H}O−H | O−O\mathrm{O{-}O}O−O | O=O\mathrm{O{=}O}O=O |
|---|---|---|---|
| Bond energy (kJ/mol\mathrm{kJ/mol}kJ/mol) | 464 | 146 | 498 |
What is the energy change for the reaction?
+206 kJ/mol+206\,\mathrm{kJ/mol}+206kJ/mol
−1280 kJ/mol-1280\,\mathrm{kJ/mol}−1280kJ/mol
−498 kJ/mol-498\,\mathrm{kJ/mol}−498kJ/mol
−206 kJ/mol-206\,\mathrm{kJ/mol}−206kJ/mol
51 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.