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Which of the following statements about surface active agents and colloids is/are incorrect?

1. Soaps and synthetic detergents always form micelles in water
2. Soaps are emulsifying agents
3. In stearate ion (C17H35COO⁻), both the hydrocarbon part C17H35 and the carboxylate part -COO⁻ are hydrophobic
4. All the above are incorrect

Correct answer: All the above are incorrect

Solution

Statement A is incorrect: surface active agents form micelles only above the critical micelle concentration (CMC), not always. Statement B is correct: soaps do act as emulsifying agents by stabilising oil-in-water emulsions. Statement C is incorrect: the -COO⁻ (carboxylate) group is hydrophilic (it is the polar, water-loving head), not hydrophobic. Therefore A and C are incorrect, but not all three — D is not completely correct either. The answer depends on what the question is testing; most standard sources mark A and C as the incorrect statements.

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