Alkanes are used as fuels. The table shows the energy released when one mole of each of six alkanes burns completely.
| Alkane | Formula | Relative formula mass | Energy released / kJ mol−1\mathrm{kJ\,mol^{-1}}kJmol−1 |
|---|---|---|---|
| methane | CH4\mathrm{CH_{4}}CH4 | 16 | 890 |
| ethane | C2H6\mathrm{C_{2}H_{6}}C2H6 | 30 | 1560 |
| propane | C3H8\mathrm{C_{3}H_{8}}C3H8 | 44 | 2220 |
| butane | C4H10\mathrm{C_{4}H_{10}}C4H10 | 58 | 2880 |
| pentane | C5H12\mathrm{C_{5}H_{12}}C5H12 | 72 | 3510 |
| hexane | C6H14\mathrm{C_{6}H_{14}}C6H14 | 86 | 4160 |
State the general formula of the alkanes.
Explain how the data in the table show that the alkanes form a homologous series.
Predict the energy released when one mole of heptane, C7H16\mathrm{C_{7}H_{16}}C7H16, burns completely. Show how you used the data.
Determine whether methane or hexane releases more energy per gram.
A camping stove burns propane. Only 60 % of the energy released by the burning propane is transferred to the water in a pan. Heating a pan of water to boiling needs 666 kJ of energy to be transferred to the water. Calculate the mass of propane that must be burned.
37 exam-style questions on Edexcel GCSE Chemistry 9.1 Fuels, covering 9.1.1 Hydrocarbons and crude oil, 9.1.2 Fractional distillation of crude oil and its fractions, 9.1.3 The alkanes as a homologous series, 9.1.4 Complete and incomplete combustion, 9.1.5 Pollutants from burning fuels, 9.1.6 Hydrogen as a fuel and non-renewable fossil fuels, and 9.1.7 Cracking of larger alkanes. Each one has a worked solution and a mark scheme showing where the marks go.