JIPMER Jipmer Medical Solved Paper-2007

  • question_answer
    At \[25{}^\circ C,\] the dissociation constant of a base, BOH, is \[1.0\times {{10}^{-12}}\]. The concentration of hydroxyl ions in 0.01 M aqueous solution of the base would be

    A)  \[2.0\times {{10}^{-6}}mol\,{{L}^{-1}}\]

    B)         \[1.0\times {{10}^{-5}}mol\,{{L}^{-1}}\]

    C)         \[1.0\times {{10}^{-6}}mol\,{{L}^{-1}}\]

    D)         \[1.0\times {{10}^{-7}}mol\,{{L}^{-1}}\]

    Correct Answer: D

    Solution :

    Base BOH is dissociated as follows \[BOH{{B}^{+}}+O{{H}^{-}}\] So, the dissociation constant of BOH base \[{{K}_{b}}=\frac{[{{B}^{+}}]\,[O{{H}^{-}}]}{[BOH]}\]       ?(i) At equilibrium \[[{{B}^{+}}]=[O{{H}^{-}}]\] \[\therefore \]  \[{{K}_{b}}=\frac{{{[O{{H}^{-}}]}^{2}}}{[BOH]}\] Given that     \[{{K}_{b}}=1.0\times {{10}^{-12}}\] and \[[BOH]=0.01\,M\] Thus      \[1.0\times {{10}^{-12}}=\frac{{{[O{{H}^{-}}]}^{2}}}{0.01}\] \[{{[O{{H}^{-}}]}^{2}}=1\times {{10}^{-14}}\] \[[O{{H}^{-}}]=1.0\times {{10}^{-7}}\,mol\,{{L}^{-1}}\]


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