The alkanoic acid found in human sweat is

Analysis of the Question

The question asks for the specific alkanoic acid (carboxylic acid) that is present in human sweat. This is a factual recall question based on the properties of organic compounds commonly found in biological systems.

Concept Explanation

Alkanoic acids (also known as carboxylic acids) have the general formula C$_n$H$_{2n+1}$COOH.

• Methanoic acid (H-COOH): Found in ant stings.
• Ethanoic acid (CH$_3$COOH): Commonly known as acetic acid (vinegar).
• Propanoic acid (CH$_3$CH$_2$COOH): This is a three-carbon acid. It is a metabolic byproduct and is known to be one of the organic acids present in human sweat, contributing to its characteristic odor.

Step-by-Step Solution

1. Evaluate Option A (CH$_3$COOH): This is ethanoic acid. While it is a common organic acid, it is not the primary acid associated with the composition of human sweat.
2. Evaluate Option B (CH$_3$CH$_2$COOH): This is propanoic acid. Scientific literature identifies propanoic acid as one of the volatile fatty acids present in human sweat.
3. Evaluate Option C (H-COOH): This is methanoic acid (formic acid), which is primarily associated with insect stings.
4. Evaluate Option D (CH$_3$): This is a methyl group, not an acid. It is an alkyl radical and does not represent an alkanoic acid.

Correct Answer

The correct option is B.

Exam Tip

When dealing with organic chemistry questions about "common sources" of compounds:

• Ants/Stings $\rightarrow$ Methanoic acid (Formic acid).
• Vinegar $\rightarrow$ Ethanoic acid (Acetic acid).
• Sweat/Body Odor $\rightarrow$ Propanoic acid.
• Rancid Butter $\rightarrow$ Butanoic acid.

Memorizing these common associations will save you time during your JAMB exam!