JEE Main & Advanced Sample Paper JEE Main Sample Paper-20

  • question_answer
    How many times solubility of \[Ca{{F}_{2}}\] is decreased in \[4\times {{10}^{-3}}M\,\,KF\,\,(aq).\]solution as compare to pure water at \[{{25}^{o}}C\]. Given \[{{K}_{sp}}(Ca{{F}_{2}})=3.2\times {{10}^{-11}}\]

    A)  \[50\]                           

    B)  \[100\]

    C)  \[500\]                         

    D)  \[1000\]

    Correct Answer: B

    Solution :

     \[4{{S}^{3}}=3.2\times {{10}^{-11}}\] \[S=2\times {{10}^{-6}}\] Let solubility of \[Ca{{F}_{2}}\] is x in KF solution. \[{{K}_{sp}}=x{{(2x+4\times {{10}^{-3}})}^{2}};3.2\times {{10}^{-11}}=x\times {{10}^{-6}}\times 16\] \[x=2\times {{10}^{-6}}\]

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