Why do detergents work better than soap in hard water?
Answer and explanation
Correct answer: They form less insoluble scum with calcium and magnesium ions
The governing concept is resistance to hardness ions. In hard water, calcium and magnesium ions readily form insoluble salts with soap’s fatty-acid ions, producing scum and reducing lather. Synthetic detergents generally contain sulfonate or sulfate groups whose calcium and magnesium salts remain relatively soluble, so little precipitate forms. More detergent stays in solution to make micelles and remove grease. Therefore option A is correct; the other choices do not explain cleaning.
Frequently asked questions
What is the correct answer to this question?
They form less insoluble scum with calcium and magnesium ions
Why is this the correct answer?
The governing concept is resistance to hardness ions. In hard water, calcium and magnesium ions readily form insoluble salts with soap’s fatty-acid ions, producing scum and reducing lather. Synthetic detergents generally contain sulfonate or sulfate groups whose calcium and magnesium salts remain relatively soluble, so little precipitate forms. More detergent stays in solution to make micelles and remove grease. Therefore option A is correct; the other choices do not explain cleaning.
Which subject and chapter does this question cover?
This is a Class 10 Science question. Chapter: Carbon and its Compounds. Topic: Soaps and detergents.
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