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AFMC AFMC Solved Paper-2008

  • question_answer
    Solubility product of a salt AB is \[1\times {{10}^{-8}}\text{ }{{\text{M}}^{\text{2}}}\] in  a solution in which the concentration of \[{{\text{A}}^{\text{+}}}\] ions is \[{{10}^{-3}}\,\text{M}\text{.}\] The salt will precipitate when the concentration of \[{{\text{B}}^{-}}\] ions is kept

    A)  between \[{{10}^{-8}}\text{M}\] to \[{{10}^{-7}}\text{M}\]

    B)  between \[{{10}^{-7}}\text{M}\] to \[{{10}^{-8}}\text{M}\]

    C)  \[>{{10}^{-5}}\text{M}\]

    D)  \[<{{10}^{-8}}\text{M}\]

    Correct Answer: C

    Solution :

                     A salt is precipitated only when the product of ionic concentration is more than its solubility product. \[{{K}_{sp}}=1\times {{10}^{-8}}\] \[[{{A}^{+}}]={{10}^{-3}}\text{M}\] \[[{{B}^{-}}]=\frac{1\times {{10}^{-8}}}{{{10}^{-3}}}={{10}^{-5}}\text{M}\] So, AB will be precipitated only when the concentration of \[[{{B}^{-}}]\] is more than \[{{10}^{-5}}\,\text{M}\text{.}\]


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