Everyday Chemistry — Nature of Soap Soap is a mixture of sodium or potassium salts of which acids?

Introduction / Context:
Household soaps are classic examples of salts derived from fatty acids. Understanding their composition clarifies how soaps clean (micelle formation) and why hard water affects lathering. The question asks for the type of acid from which common soaps are made when neutralized by sodium or potassium bases.

Given Data / Assumptions:

• Soaps arise from saponification of triglycerides (fats/oils) with NaOH or KOH.
• Fatty acids in natural fats are typically long-chain monocarboxylic acids (e.g., palmitic, stearic, oleic).
• Sodium or potassium salts constitute hard and soft soaps respectively.

Concept / Approach:
In saponification, ester bonds in triglycerides are hydrolyzed to yield glycerol and the salts of fatty acids. Each fatty acid has one –COOH group (monocarboxylic). The resulting salts are sodium or potassium carboxylates (R–COO– Na+ / K+). These amphiphilic molecules form micelles that emulsify grease.

Step-by-Step Solution:

Verification / Alternative check:
Common soap labels list “sodium stearate,” “sodium palmitate,” etc., all salts of single-carboxyl group fatty acids.

Why Other Options Are Wrong:

• dicarboxylic acids / tricarboxylic acids: Not the standard fatty acids used for soap; multiple carboxyl groups would change properties and synthesis routes.
• glycerol: A byproduct (triol), not the acid.

Common Pitfalls:
Confusing glycerol (product) with the fatty acid salts (actual soap). The cleansing action is due to amphiphilic carboxylate salts, not glycerol.

Final Answer:
monocarboxylic acids