JEE Main & Advanced Chemistry Hydrogen & Its Compounds / हाइड्रोजन और इसके यौगिक Question Bank Critical Thinking Questions

  • question_answer
    Permanent hardness due to \[M{{g}^{2+}}\] ions is best removed by

    A) \[Ca{{(OH)}_{2}}\]

    B) \[N{{a}_{2}}C{{O}_{3}}\]

    C) \[N{{a}_{2}}C{{O}_{3}}+Ca{{(OH)}_{2}}\]

    D) None of these

    Correct Answer: C

    Solution :

    \[Ca{{(OH)}_{2}}\] removes the permanent hardness due to \[M{{g}^{2+}}\] ion, but it produces \[C{{a}^{2+}}\] ions which are removed by \[N{{a}_{2}}C{{O}_{3}}\]. \[M{{g}^{2+}}+Ca{{(OH)}_{2}}\to Mg{{(OH)}_{2}}\downarrow +C{{a}^{2+}}\] \[C{{a}^{2+}}+N{{a}_{2}}C{{O}_{3}}\to CaC{{O}_{3}}\downarrow +2N{{a}^{+}}\] \[Ca{{(OH)}_{2}}\] or \[N{{a}_{2}}C{{O}_{3}}\] alone cannot remove the permanent hardness.


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