Q1. [3] medium thorough-understanding
[short_answer] Ethanol is warmed with ethanoic acid in the presence of a few drops of concentrated sulphuric acid. A sweet-smelling compound 'P' is formed. 'P' is then treated with sodium hydroxide solution to give compound 'Q' and ethanol. (i) Identify 'P' and 'Q', and name the type of reaction that forms each of them. (ii) Write balanced chemical equations for both reactions. (iii) State one industrial application of the reaction that produces 'Q'.
Generated by claude-sonnet-4-6 · 2026-06-26 01:11 · grounding rag
Model Answer
(i)
- P = Ethyl ethanoate (an ester); formed by esterification reaction.
- Q = Sodium ethanoate (sodium acetate); formed by saponification reaction.
(ii)
Formation of P (Esterification):
$$\text{CH}_3\text{COOH} + \text{C}_2\text{H}_5\text{OH} \xrightarrow{\text{Conc. H}_2\text{SO}_4} \text{CH}_3\text{COOC}_2\text{H}_5 + \text{H}_2\text{O}$$
Formation of Q (Saponification):
$$\text{CH}_3\text{COOC}_2\text{H}_5 + \text{NaOH} \rightarrow \text{CH}_3\text{COONa} + \text{C}_2\text{H}_5\text{OH}$$
(iii) Saponification is used industrially in soap making — fats/oils are hydrolysed with sodium hydroxide to produce soap (sodium salts of fatty acids) and glycerol.
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Explanation
- Examiners expect you to correctly name both compounds and both reaction types — these fetch separate marks.
- The balanced equations must show the catalyst (conc. H₂SO₄) for esterification; forgetting it costs marks.
- For the industrial application, "soap making / saponification of fats and oils" is the standard accepted answer. Do not confuse this with the saponification of the ester in part (ii) — the principle is the same but applied to triglycerides in industry.