CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2011

  • question_answer
    The solubility product\[({{K}_{sp}})\]of the following compounds are given at\[25{}^\circ C\] Compounds                       \[{{K}_{sp}}\] \[AgCl\]                                \[1.1\times {{10}^{-10}}\] \[AgI\]                 \[1.0\times {{10}^{-16}}\] \[PbCr{{O}_{4}}\]             \[4.0\times {{10}^{-14}}\] \[A{{g}_{2}}C{{O}_{3}}\]             \[8.0\times {{10}^{-12}}\] The most soluble and least soluble compounds are

    A) \[AgCl\]and\[PbCr{{O}_{4}}\]    

    B)  \[AgI\] and\[A{{g}_{2}}C{{O}_{3}}\]

    C) \[AgCl\]and\[A{{g}_{2}}C{{O}_{3}}\]

    D)       \[A{{g}_{2}}C{{O}_{3}}\]and \[AgI\]

    E) \[A{{g}_{2}}C{{O}_{3}}\]and \[PbCr{{O}_{4}}\]

    Correct Answer: D

    Solution :

     (i) \[AgCl(s)\underset{s}{\mathop{A{{g}^{+}}}}\,(aq)+\underset{s}{\mathop{C{{l}^{-}}}}\,(aq)\] \[{{K}_{sp}}=[A{{g}^{+}}][C{{l}^{-}}]\] \[=s\times s={{s}^{2}}\]                 \[{{K}_{sp}}=1.1\times {{10}^{-10}}\](given) \[\therefore \]  \[{{s}^{2}}=1.1\times {{10}^{-10}}\] or          \[s=1.04\times {{10}^{-5}}mol\,{{L}^{-1}}\] (ii) \[AgI\underset{s}{\mathop{A{{g}^{+}}}}\,+\underset{s}{\mathop{{{I}^{-}}}}\,\]                 \[{{K}_{sp}}=[A{{g}^{+}}][{{I}^{-}}]\]                 \[=s\times s={{s}^{2}}\]                 \[{{K}_{sp}}={{s}^{2}}=1.0\times {{10}^{-16}}\] or           \[s=1.0\times {{10}^{-8}}mol\,{{L}^{-1}}\] (iii) \[PbCr{{O}_{4}}\underset{s}{\mathop{P{{b}^{2+}}}}\,+\underset{s}{\mathop{CrO_{4}^{2-}}}\,\] \[{{K}_{sp}}=[P{{b}^{2+}}][CrO_{4}^{2-}]\] \[=s\times s={{s}^{2}}\] \[{{K}_{sp}}={{s}^{2}}=4.0\times {{10}^{-14}}\] or            \[s=2.0\times {{10}^{-7}}mol\text{ }{{L}^{-1}}\] (iv) \[A{{g}_{2}}C{{O}_{3}}\underset{s}{\mathop{2A{{g}^{+}}}}\,+\underset{s}{\mathop{CO_{3}^{2-}}}\,\]                 \[=4{{s}^{3}}\] \[{{K}_{sp}}=[A{{g}^{+}}][CO_{3}^{2-}]\]                 \[={{(2s)}^{2}}\times s=4{{s}^{3}}\]                 \[{{K}_{sp}}=4{{s}^{3}}=8.0\times {{10}^{-12}}\] Or           \[s=1.26\times {{10}^{-4}}mol\,{{L}^{-1}}\]


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