Ethanol can be produced by fermentation or by hydration of ethene. Describe the process of fermentation to produce ethanol, and give one advantage of using fermentation rather than hydration of ethene to produce ethanol.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Ethanol is a member of the homologous series of alcohols. It is widely used as a fuel and as a solvent. Two industrial methods exist for its production.
Model answer (5 marks)
1. A sugar (glucose) solution is used as the reactant.
2. Yeast is the biological catalyst that carries out the fermentation.
3. The reaction is performed in the absence of oxygen (anaerobically).
4. The process is carried out at a warm or moderate temperature, about 30–40 °C.
5. Fermentation uses a renewable raw material – sugar from plants – whereas hydration of ethene uses a finite, non‑renewable resource (crude oil/ethene from cracking).
2. Yeast is the biological catalyst that carries out the fermentation.
3. The reaction is performed in the absence of oxygen (anaerobically).
4. The process is carried out at a warm or moderate temperature, about 30–40 °C.
5. Fermentation uses a renewable raw material – sugar from plants – whereas hydration of ethene uses a finite, non‑renewable resource (crude oil/ethene from cracking).
Examiner tips
- Use the exact terms: glucose, yeast, anaerobically, 30–40 °C, renewable raw material.
- Show the five points in a clear, numbered list to match the mark scheme.
- Mention the advantage (renewable vs non‑renewable) as the final point.
Common mistakes
- Writing oxygen instead of anaerobic conditions.
- Omitting the temperature range or giving an incorrect value.
- Failing to state that glucose is the starting material or that yeast is the catalyst.
Mark scheme (5 marks)
- Sugar (glucose) solution is used as the reactant / starting material
- Yeast is used as the biological catalyst / yeast carries out the fermentation
- The process must be carried out in the absence of oxygen / anaerobically
- Fermentation is carried out at a warm / moderate temperature (approximately 30–40 °C)
- Fermentation uses a renewable raw material (sugar/glucose from plants) whereas hydration of ethene uses a finite/non-renewable resource (crude oil / ethene from cracking)
Key terms in this question
Related
- All AQA A-Level Chemistry (7405) revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
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