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2025 O Level Chem P1 Q34 — Organic Chemistry / Biofuels Solution

Organic Chemistry / Biofuels 2025 O Level Pure Chemistry · Paper 1 · Q34

Question

Which structure shows a substance used as a biofuel? Question diagram

Question diagram

AO=C=O (carbon dioxide structure)
BH—C(H)(H)—C(H)(H)—O—H (two-carbon alcohol structure)
CH—C(H)—C(=O)—O—H (carboxylic acid structure with two carbons)
DH—C(H)(H)—C(H)=C(H)—H (alkene structure)

Correct answer: B

Video Solution

Explanation

Answer: B. A biofuel is a fuel produced from living organisms, the most common being ethanol from fermentation of sugars.

Option B shows the structure of ethanol (\(\text{C}_2\text{H}_5\text{OH}\)) — two carbons with an –OH group. Ethanol is the standard answer for 'biofuel' in O-Level chemistry.

A (\(\text{CO}_2\)) is the product of combustion, not a fuel itself.
C is a carboxylic acid (–COOH group) — not a fuel.
D is an alkene (a hydrocarbon with a C=C double bond) — alkenes are not biofuels; they are usually petroleum products.

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