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    Question

    Hard water does not give lather with soap due to the

    presence of which ions?
    A Na⁺ and K⁺ Correct Answer Incorrect Answer
    B Mg²⁺ and Ca²⁺ Correct Answer Incorrect Answer
    C Cl⁻ and SO₄²⁻ Correct Answer Incorrect Answer
    D Fe²⁺ and Zn²⁺ Correct Answer Incorrect Answer

    Solution

    Hard water contains dissolved calcium (Ca²⁺) and magnesium (Mg²⁺) ions, which react with soap molecules (sodium or potassium salts of fatty acids) to form insoluble scum instead of forming lather. This makes it difficult for soap to work effectively.

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