J & K CET Engineering J and K - CET Engineering Solved Paper-2010

  • question_answer
    Why calcium ion makes water hard but sodium ion does not?                       

    A)  Calcium forms insoluble compound with stearate ion present in soap

    B)  Sodium forms insoluble compound with stearate ion present in soap

    C)  Calcium forms soluble compound with stearate ion present in soap

    D)  Both calcium and sodium forms insoluble compound with stearate ion present in soap

    Correct Answer: A

    Solution :

     Soaps are sodium or potassium salts of higher fatty acids, eg, sodium stearate. Sodium stearate or sodium and potassium salts of higher fatty acids are water soluble but the corresponding magnesium and calcium salts are not. Thus, these make water hard.


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