Ethanol can be produced by two different industrial methods: fermentation of glucose, and the hydration of ethene. Describe fermentation as a method of producing ethanol, and state one advantage and one disadvantage of using fermentation compared with the hydration of ethene.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (5 marks)
Glucose is converted to ethanol and carbon dioxide by yeast:
C6H12O6 → 2 C2H5OH + 2 CO2
The reaction is carried out at warm temperatures (≈25–37 °C) and in anaerobic conditions. After fermentation the ethanol is separated from the aqueous mixture by distillation.
Advantage: fermentation uses a renewable raw material (glucose from plants/biomass) and is a sustainable, carbon‑neutral process.
Disadvantage: fermentation is a slow, batch process that produces a dilute ethanol solution, requiring energy‑intensive distillation to concentrate the product.
C6H12O6 → 2 C2H5OH + 2 CO2
The reaction is carried out at warm temperatures (≈25–37 °C) and in anaerobic conditions. After fermentation the ethanol is separated from the aqueous mixture by distillation.
Advantage: fermentation uses a renewable raw material (glucose from plants/biomass) and is a sustainable, carbon‑neutral process.
Disadvantage: fermentation is a slow, batch process that produces a dilute ethanol solution, requiring energy‑intensive distillation to concentrate the product.
Examiner tips
- Use the reaction equation and mention yeast, temperature and anaerobic conditions; include distillation; give one advantage and one disadvantage; keep answer concise and to the point.
Common mistakes
- Omitting the reaction equation or the need for anaerobic conditions; confusing fermentation with distillation; giving non‑specific advantages such as ‘cheap’ without linking to renewability.
Mark scheme (5 marks)
- Glucose is broken down / converted to ethanol (and carbon dioxide) by yeast / enzymes
- The reaction requires warm/suitable temperatures (approximately 25–37 °C) / anaerobic (absence of oxygen) conditions
- The ethanol produced must be separated / purified by distillation
- One advantage: fermentation uses a renewable raw material (glucose/sugar/plants/biomass) / is a sustainable/carbon-neutral process
- One disadvantage: fermentation is a slow/batch process / produces a dilute solution of ethanol / requires distillation to concentrate the product
Key terms in this question
Related
- All Eduqas A-Level Chemistry revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
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