The table shows properties of some fuels - HSC - SSCE Chemistry - Question 25 - 2004 - Paper 1

When evaluating ethanol as an alternative fuel, several key factors from the table are considered:

1. Heat of Combustion

Ethanol has a heat of combustion of 29.7 kJ g⁻¹, which is significantly lower than methane (55.6 kJ g⁻¹), propane (50.3 kJ g⁻¹), and octane (47.9 kJ g⁻¹). This lower energy release suggests that ethanol may be less efficient as a fuel compared to these alternatives.

2. Boiling Point

The boiling point of ethanol is 78.3 °C, which is lower than octane (125.7 °C) but higher than methane (–161.5 °C) and propane (–42.1 °C). Lower boiling points can mean that ethanol vaporizes more easily, which could benefit its use in certain applications. However, the higher boiling point compared to some other fuels may limit its usability in extremely cold environments.

3. Environmental Considerations

Ethanol, derived from renewable sources through fermentation or hydration of ethene, can be regarded as a more sustainable fuel when compared to fossil fuels. Its ability to be produced from agricultural feedstock supports the transition towards greener fuel options.

Conclusion

While ethanol presents advantages in terms of sustainability, its lower heat of combustion compared to other fuels suggests it may not provide the same energy efficiency. Therefore, while it is a viable alternative fuel, its application may be more suited for minor or supplementary uses rather than as a primary fuel source for high-energy demands.