Propane burns completely in oxygen.
C3H8+5O2→3CO2+4H2O \mathrm{C_3H_8 + 5O_2 \rightarrow 3CO_2 + 4H_2O} C3H8+5O2→3CO2+4H2OEach propane molecule contains eight C−H\mathrm{C{-}H}C−H bonds and two C−C\mathrm{C{-}C}C−C bonds.
| Bond | C−C\mathrm{C{-}C}C−C | C−H\mathrm{C{-}H}C−H | O=O\mathrm{O{=}O}O=O | C=O\mathrm{C{=}O}C=O | O−H\mathrm{O{-}H}O−H |
|---|---|---|---|---|---|
| Bond energy (kJ/mol\mathrm{kJ/mol}kJ/mol) | 347 | 413 | 498 | 805 | 463 |
The energy change when one mole of methane burns is -814 kJ/mol.
A supplier claims that burning one mole of propane releases more than three times as much energy as burning one mole of methane.
Calculate the energy change for the combustion of propane.
Evaluate the supplier's claim. Use the data and your answer to part (a).
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.