Ethanol (C₂H₅OH) is an organic compound found in alcoholic drinks and is also used as a fuel. Explain why ethanol is classified as an alcohol and describe the products formed when ethanol undergoes complete combustion.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Ethanol has the molecular formula C₂H₅OH and burns readily in air.
Model answer (5 marks)
Ethanol contains a hydroxyl (–OH) group, which is the defining functional group of alcohols. Because it has carbon and hydrogen atoms, it is also an organic compound. During complete combustion in air, ethanol reacts with oxygen to give carbon dioxide (CO₂) and water (H₂O).
Examiner tips
- Use the term ‘hydroxyl group’ to show you know the functional group; mention carbon and hydrogen to justify it being organic; state the balanced equation or products CO₂ and H₂O; keep answer concise and use correct terminology.
- Remember to link the OH group to the alcohol definition and to list both combustion products.
Mark scheme (5 marks)
- Ethanol contains a hydroxyl / OH group
- The OH / hydroxyl group is the functional group that defines alcohols
- Ethanol is also a hydrocarbon / contains carbon and hydrogen (in addition to oxygen) — accept: it is an organic compound containing carbon
- Complete combustion produces carbon dioxide
- Complete combustion also produces water
Key terms in this question
Related
- All WJEC A-Level Chemistry (Wales) revision notes →
- How to answer a "Explain and Describe" question →
- Decode the mark scheme abbreviations →
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