One reaction involving fuels is the combustion of methanol. The balanced symbol equation for this reaction is:
2CH3OH+3O2→2CO2+4H2O 2\text{CH}_3\text{OH} + 3\text{O}_2 \rightarrow 2\text{CO}_2 + 4\text{H}_2\text{O} 2CH3OH+3O2→2CO2+4H2OA molecule of methanol (CH3OH\text{CH}_3\text{OH}CH3OH) contains three C−H\text{C}-\text{H}C−H bonds, one C−O\text{C}-\text{O}C−O bond, and one O−H\text{O}-\text{H}O−H bond. A molecule of oxygen (O2\text{O}_2O2) contains one O=O\text{O}=\text{O}O=O bond. A molecule of carbon dioxide (CO2\text{CO}_2CO2) contains two C=O\text{C}=\text{O}C=O bonds. A molecule of water (H2O\text{H}_2\text{O}H2O) contains two O−H\text{O}-\text{H}O−H bonds.
The table below shows the average bond energies:
| Bond | Bond energy (kJ/mol) |
|---|---|
| C−H\text{C}-\text{H}C−H | 412 |
| C−O\text{C}-\text{O}C−O | 358 |
| O−H\text{O}-\text{H}O−H | 465 |
| O=O\text{O}=\text{O}O=O | 498 |
| C=O\text{C}=\text{O}C=O | 799 |
Calculate the energy transferred when all the bonds form in the products.
The energy transferred when all the bonds break in the reactants is 5612 kJ/mol. Use your answer to part (i) to calculate the overall energy change for this reaction.