Q1. [2] medium thorough-understanding
Ethanol, when heated with concentrated sulphuric acid at 443 K, undergoes a chemical change. (i) What role does the concentrated sulphuric acid play in this reaction? (ii) Name the product formed and classify it as saturated or unsaturated. Write the chemical equation for the reaction.
Generated by claude-sonnet-4-6 · 2026-06-26 01:11 · grounding rag
Model Answer
(i) Concentrated sulphuric acid acts as a dehydrating agent — it removes water from ethanol.
(ii) The product formed is ethene (CH₂=CH₂). It is an unsaturated hydrocarbon (contains a C=C double bond).
Chemical equation:
$$\text{CH}_3\text{CH}_2\text{OH} \xrightarrow{\text{Hot conc. H}_2\text{SO}_4,\ 443\text{ K}} \text{CH}_2{=}\text{CH}_2 + \text{H}_2\text{O}$$
Source: Carbon and its Compounds, Section 4.4.1 (Properties of Ethanol)
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Explanation
- The key term examiners look for is "dehydrating agent" — not catalyst or oxidising agent.
- Ethene must be correctly identified as unsaturated because of its C=C double bond; saturated compounds have only single bonds.
- Always write the balanced chemical equation with the condition (hot conc. H₂SO₄, 443 K) shown above the arrow.
- This reaction is called dehydration of ethanol.