Ethanoic acid is heated with ethanol in the presence of concentrated sulphuric acid to give ethyl ethanoate. Which of the following will increase the amount of ethyl ethanoate obtained?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Distilling off the ethyl ethanoate as soon as it is formed
Esterification is a reversible reaction. The ester and water can react to give back the acid and the alcohol, so the reaction reaches an equilibrium:
\( \displaystyle \ce{CH3COOH + C2H5OH <=> CH3COOC2H5 + H2O} \quad (\text{conc. }\ce{H2SO4}) \)
If the ester (or the water) is taken out as soon as it forms, the backward reaction cannot occur, and the equilibrium shifts to the right, so more of the acid and the alcohol change into ester.
Why the other options are incorrect
Option (1) Using a smaller amount of ethanol for the same amount of ethanoic acid — Incorrect. Ethanol is a reactant; with less of it the equilibrium lies further to the left, so less ester is formed.
Option (2) Using dilute sulphuric acid in place of concentrated sulphuric acid — Incorrect. Dilute acid brings water, a product, into the mixture; this pushes the equilibrium to the left and hydrolyses some ester back to the acid and the alcohol.
Option (3) Leaving out the concentrated sulphuric acid — Incorrect. The mineral acid is the catalyst; without it the reaction is very slow, and a catalyst never increases the amount of product at equilibrium either way.
NCERT (2026-27 edition):
8.9.2 Reactions Involving Cleavage of C–OH Bond – “2. Esterification
Carboxylic acids are esterified with alcohols or phenols in the presence of a mineral acid such as concentrated H2SO4 or HCl gas as a catalyst.”
\( \displaystyle \ce{RCOOH + R'OH <=> RCOOR' + H2O} \quad (\ce{H+}) \)
Exercises – “8.18 Give plausible explanation for each of the following: …(iii) During the preparation of esters from a carboxylic acid and an alcohol in the presence of an acid catalyst, the water or the ester should be removed as soon as it is formed.”