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Question
Why does hard water not form lather with soap?
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Solution
With soap, hard water generates scum/precipitate. Soap containing sodium stearate \[\ce{(C117H35COONa)}\] interacts with hard water to form calcium and magnesium stearate (\[\ce{Ca/Mg}\] stearate). As a result, it is unsuitable for laundering. Because of the deposition of salts in the form of scale, it is also hazardous to boilers.
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