WAEC 2011 Chemistry · Question 16

Which of the following compounds would react with ethanoic acid to give a sweet smelling liquid?

Options

A.Alkane
B.Alkanol
C.Alkanal
D.Alkyne

Answer: B. Alkanol

Explanation written with AI and checked against the answer key

Analyze the question: A sweet-smelling (fruity) liquid is the typical description of an ester. So we need to find which compound reacts with ethanoic acid to form an ester.

Concept: Esterification is the reaction between a carboxylic acid and an alcohol (alkanol) in the presence of concentrated H₂SO₄ as catalyst, producing an ester and water.

General equation:

RCOOH + R'OH ⇌ RCOOR' + H₂O

Example with ethanoic acid and ethanol:

CH₃COOH + C₂H₅OH ⇌ CH₃COOC₂H₅ + H₂O (conc. H₂SO₄, heat)

The product, ethyl ethanoate, has a sweet, fruity smell.

Checking the options:

A. Alkane: Saturated hydrocarbons are unreactive toward carboxylic acids. No reaction.
B. Alkanol: Reacts with ethanoic acid to form an ester. Correct.
C. Alkanal: Aldehydes do not form esters with carboxylic acids.
D. Alkyne: Unsaturated hydrocarbons undergo addition reactions, and they do not form esters with ethanoic acid under normal conditions.

Exam tip: Remember "Acid + Alcohol → Ester + Water." Whenever you see "sweet smell" or "fruity smell" in a question, think ester, and look for the alkanol (alcohol) option.

AI can make mistakes. Report anything that looks wrong.