Comparing the two methods of producing ethanol
4 marks · NormalThe table below gives information about two methods of making ethanol.
| Feature | Fermentation | Hydration of Ethene |
|---|---|---|
| Raw material | Corn or sugar cane (renewable) | Ethene from crude oil (non-renewable) |
| Process type | Batch, slow | Continuous, fast |
| Energy requirement | Low | High |
| Product purity | Impure, needs further processing | Very pure |
Based on the table, give two reasons why a country with limited access to crude oil and plenty of farmland might prefer fermentation to make ethanol.
Give one disadvantage to this country of using fermentation rather than hydration of ethene.
Suggest one way the country could improve the efficiency of ethanol production using fermentation.
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(a) Has renewable raw materials from farmland; does not need to import crude oil; can use slow, low-energy process suited to local resources.
(b) Fermentation is slower; produces impure ethanol and needs further processing.
(c) Use enzymes or genetically modified yeast to speed up reaction; keep optimal temperature; use larger or more frequent batches.
Common mistakes: Giving general answers not based on the data in the table.; Confusing which method is renewable.
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Correctly identifies use of renewable crops/farmland as an advantage.
B2 (a) · 1 mark · Correctly identifies not needing crude oil as an advantage.
B3 (b) · 1 mark · Correctly states a disadvantage of fermentation (e.g., slower, produces impure ethanol).
B4 (c) · 1 mark · Suggests a reasonable way to improve efficiency (e.g., use enzymes, maintain optimal temperature, increase batch size or frequency).
Worked solution
a. The country has access to renewable crops (e.g., corn, sugar cane) and does not need to rely on non-renewable crude oil.
b. Fermentation is slower and produces ethanol that is less pure, requiring further processing.
c. The country could improve efficiency by using enzymes or genetically modified yeast, maintaining an optimal temperature, or increasing the number or size of batches.