iGCSE Chemistry 0620 Extended - 11.7 Carboxylic acids- Exam Style Questions Paper 2- New Syllabus
▶️ Answer/Explanation
The reaction between methanol (CH3OH) and ethanoic acid (CH3COOH) produces the ester methyl ethanoate (CH3COOCH3) and water. The ester functional group is −COO−. The displayed formula must show the carbon-oxygen double bond (C=O) and the C−O single bond connecting the methyl group from the methanol. The correct structure has the ester linkage with the carbonyl group attached to a methyl group on one side and a methoxy group on the other.
✅ Answer: (C)
✅ Answer: (C)
▶️ Answer/Explanation
Correct Answer: D
Explanation: When ethanol (in alcoholic drinks or cider) is exposed to air in the presence of certain bacteria (Acetobacter), it is oxidised to ethanoic acid. The dilute solution of ethanoic acid produced is known as vinegar. This is the bacterial oxidation process: \(\mathrm{CH_3CH_2OH + O_2 \rightarrow CH_3COOH + H_2O}\).
✅ Vinegar (ethanoic acid) is produced.
▶️ Answer/Explanation
Ethanol is oxidised to ethanoic acid by acidified potassium manganate(VII): the purple colour of \(\mathrm{KMnO_4}\) changes to colourless. This is an oxidation reaction.
(A) is false — ethanol is oxidised, not reduced.
(B) is false — the correct formula for magnesium ethanoate is \(\mathrm{(CH_3COO)_2Mg}\).
(C) is false — ethanoic acid + methanol produces methyl ethanoate, not ethyl methanoate.
✅ Answer: (D)
(A) is false — ethanol is oxidised, not reduced.
(B) is false — the correct formula for magnesium ethanoate is \(\mathrm{(CH_3COO)_2Mg}\).
(C) is false — ethanoic acid + methanol produces methyl ethanoate, not ethyl methanoate.
✅ Answer: (D)