Soap cannot be used with hard water, because _________________?

Correct answer: B. They form insoluble calcium soaps which precipitate

  • A. Hard water contains sulphate
  • B. They form insoluble calcium soaps which precipitate
  • C. They attract back the removed dirt
  • 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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