Making ethanol by fermentation
3 marks · NormalEthanol can be produced by fermentation or by the hydration of ethene.
Explain two advantages and one disadvantage of making ethanol by fermentation instead of from ethene.
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Advantages: (i) Uses renewable resources such as sugar cane or corn; (ii) Does not require expensive equipment or high temperature/pressure. Disadvantage: (i) Produces a dilute solution so ethanol must be separated (purified) by distillation.
Also accept: Fermentation is less energy intensive; Fermentation can be done at lower temperature; Fermentation is slower; Fermentation uses more land
Common mistakes: Mixing up batch/continuous process as advantage/disadvantage; Confusing all renewable resources
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Marking points
B1 · 1 mark · Explains one correct advantage of fermentation (e.g., renewable resource).
B2 · 1 mark · Explains a second correct advantage.
B3 · 1 mark · Explains one correct disadvantage of fermentation (e.g., dilute product).
Worked solution
Fermentation uses renewable resources like plant sugars and can be done at lower temperatures and pressures, so it uses less energy. However, it produces a dilute ethanol solution, so distillation is needed, making the process less efficient.