Soap cannot be used with hard water, because _________________?
Correct answer: C. They form insoluble calcium soaps which precipitate
- A. Hard water contains sulphate
- B. They attract back the removed dirt
- C. They form insoluble calcium soaps which precipitate
- D. None of these
Explanation
Calcium and magnesium ions in hard water react with soap to form insoluble salts, commonly called soap scum, which precipitate instead of cleaning effectively. Sulphate alone is not the fundamental reason for soap's poor performance.
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