NEET AIPMT SOLVED PAPER SCREENING 2012

  • question_answer
    pH of a saturated solution of \[Ba{{(OH)}_{2}}\] is 12. The value of solubility product K of \[Ba{{(OH)}_{2}}\] is

    A) \[3.3\times {{10}^{-7}}\]

    B)                        \[5.0\times {{10}^{-7}}\]              

    C)        \[4.0\times {{10}^{-6}}\]              

    D)        \[5.0\times {{10}^{-6}}\]

    Correct Answer: B

    Solution :

    Given, \[pH\]of\[Ba{{(OH)}_{2}}=12\] \[\therefore \]  \[pOH=14-pH\]                 \[=14-12=2\] We know that, \[pOH=-\log [O{{H}^{-}}]\]                 \[2=-\log [O{{H}^{-}}]\] \[[O{{H}^{-}}]=\text{antilog}\,\text{(-2)}\] \[[O{{H}^{-}}]=1\times {{10}^{-2}}\] \[Ba{{(OH)}_{2}}\]dissolves in water as \[\underset{s\,mol\,{{L}^{-1}}}{\mathop{Ba{{(OH)}_{2}}}}\,(s)\underset{s\,}{\mathop{B{{a}^{2+}}}}\,+\underset{2s\,}{\mathop{2O{{H}^{-}}}}\,\] \[\therefore \]  \[[O{{H}^{-}}]=2s=1\times {{10}^{-2}}\]                 \[[B{{a}^{2+}}]=\frac{[O{{H}^{-}}]}{2}=\frac{1\times {{10}^{-2}}}{2}\]                 \[{{K}_{sp}}=[B{{a}^{2+}}]{{[O{{H}^{-}}]}^{2}}\]                 \[=\left( \frac{1\times {{10}^{-2}}}{2} \right){{(1\times {{10}^{-2}})}^{2}}\]                 \[=0.5\times {{10}^{-6}}=5\times {{10}^{-7}}\]


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