MGIMS WARDHA MGIMS WARDHA Solved Paper-2003

  • question_answer
    The values of\[{{K}_{sp}}\]for\[CuS,A{{g}_{2}}S\]and\[HgS\]are \[{{10}^{-31}},~{{10}^{42}}\]and\[{{10}^{-54}}\]respectively. The correct order of their solubility in water is:

    A) \[A{{g}_{2}}S>HgS>CuS\]

    B) \[HgS>CuS>A{{g}_{2}}S\]

    C) \[HgS>A{{g}_{2}}S>CuS\]

    D) \[A{{g}_{2}}S>CuS>HgS\]

    Correct Answer: D

    Solution :

                     Solubility product\[({{K}_{sp}})\]of\[CuS={{10}^{-31}}\] liability of             \[CuS=\sqrt{{{K}_{sp}}}=\sqrt{{{10}^{-31}}}\] \[=3.16\times {{10}^{-16}}mol/lit\] Similarly, solubility of\[A{{g}_{2}}S\] \[=\sqrt[3]{\frac{{{K}_{sp}}}{4}}\] \[(\because for\,A{{g}_{2}}S,4{{s}^{3}}={{K}_{sp}})\] \[=\sqrt{\frac{{{10}^{-42}}}{4}}\] \[=6.3\times {{10}^{-15}}mol/litre\] Solubility of\[HgS=\sqrt{{{K}_{sp}}}\] \[=\sqrt{{{10}^{-54}}}\] \[={{10}^{-27}}mol/lit\] Hence, the correct order of solubility is \[A{{g}_{2}}S>CuS>HgS\]


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