Butanol can be produced by two different methods: fermentation of sugars and the reaction of butene with steam. Compare these two methods of producing butanol, giving TWO differences between them.

Pearson Edexcel International GCSE Chemistry (4CH1) — 4.5 Alcohols · Compare · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Butanol is an alcohol used as an industrial solvent and as a biofuel. It can be produced from renewable or non-renewable sources depending on the manufacturing method chosen.

Model answer (4 marks)

1. Fermentation uses a biological catalyst (yeast or enzymes) whereas the reaction of butene with steam uses a chemical catalyst (acid, e.g. phosphoric acid). 2. Fermentation starts from a renewable feed‑stock (sugars/biomass) whereas the steam‑hydration of butene uses a non‑renewable feed‑stock (butene derived from crude oil).

Examiner tips

Use the word ‘uses’ to show the comparison; include both sides of each comparison in one sentence.
Mention the type of catalyst and the source of the starting material for each method.
Keep the answer concise – 4 marks only.
Use UK spelling (e.g. ‘catalyst’).

Common mistakes

Writing only one side of a comparison (e.g. ‘Fermentation uses a biological catalyst’ without mentioning the chemical catalyst).
Confusing the starting material of the steam‑hydration step (saying it uses sugars).
Using vague terms like ‘natural’ instead of ‘renewable’ or ‘non‑renewable’.

Mark scheme (4 marks)

Fermentation uses a biological catalyst (yeast / enzyme) whereas the reaction of butene with steam uses a chemical catalyst (phosphoric acid / acid catalyst)
Award second mark for a valid comparison of catalyst — mark as a pair with point 1 only if both sides of the comparison are stated
Fermentation uses a renewable starting material (sugars / glucose / biomass) whereas hydration of butene uses a non-renewable starting material (butene derived from crude oil / cracking)
Fermentation is carried out at low / room temperature (~30–40 °C) whereas the reaction of butene with steam requires a high temperature / elevated temperature and high pressure

Key terms in this question

fermentation