Science (086) — AI-generated practice question

(i) This is called an esterification reaction. When ethanoic acid reacts with ethanol in the presence of concentrated H₂SO₄ (as acid catalyst), an ester called ethyl ethanoate (CH₃COOC₂H₅) is formed along with water.

$$\text{CH}_3\text{COOH} + \text{C}_2\text{H}_5\text{OH} \xrightarrow{\text{conc. H}_2\text{SO}_4} \text{CH}_3\text{COOC}_2\text{H}_5 + \text{H}_2\text{O}$$

Esters are sweet-smelling substances used in perfumes and flavouring agents.

(ii) When ethyl ethanoate is treated with NaOH solution, it is converted back to ethanol and sodium ethanoate (sodium salt of ethanoic acid). This reaction is called saponification.

$$\text{CH}_3\text{COOC}_2\text{H}_5 + \text{NaOH} \rightarrow \text{C}_2\text{H}_5\text{OH} + \text{CH}_3\text{COONa}$$

Source: Chapter 4, Section 4.4.2 (Properties of Ethanoic Acid – Esterification Reaction)

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• Part (i) carries ~2 marks: name the reaction (esterification), name the product (ethyl ethanoate), and write the equation. Don't forget to mention the role of H₂SO₄ as a catalyst.
• Part (ii) carries ~1 mark: name the reaction (saponification) and state both products. Writing the equation adds precision.
• Examiners specifically look for the term saponification — it connects to soap-making and is a key vocabulary word in this chapter.