BCECE Medical BCECE Medical Solved Papers-2006

  • question_answer
    Some chemists at ISRO wished to prepare a saturated solution of a silver compound and they wanted it to have the highest concentration of silver ion possible. Which of the following compounds, would they use? \[{{K}_{sp}}(AgCl)=1.8\times {{10}^{-10}}\], \[{{K}_{sp}}(AgBr)=5.0\times {{10}^{-13}}\], \[{{K}_{sp}}(A{{g}_{2}}Cr{{O}_{4}})=2.4\times {{10}^{-12}}\]

    A)  \[AgCl\]

    B)  \[AgBr\]

    C)  \[AgCr{{O}_{4}}\]

    D)  None of these

    Correct Answer: C

    Solution :

    For binary salts (like \[AgCl,\,AgBr\]),                 \[s=\sqrt{{{K}_{sp}}}\] \[\therefore \] Solubility of \[AgCl=\sqrt{1.8\times {{10}^{-10}}}\]                 \[=1.35\times {{10}^{-7}}mol/L\] Solubility of \[AgBr=\sqrt{5.0\times {{10}^{-13}}}\]                 \[=7.1\times {{10}^{-7}}mol/L\] For, \[A{{g}_{2}}Cr{{O}_{4}},\,{{K}_{sp}}=4{{s}^{3}}\] \[\therefore \] Solubility of \[A{{g}_{2}}Cr{{O}_{4}}\]                 \[=\sqrt[3]{\frac{{{K}_{sp}}}{4}}=\sqrt[3]{\frac{2.4\times {{10}^{-12}}}{4}}\]                 \[=\sqrt[3]{600\times {{10}^{-15}}}\]                 \[=8.44\times {{10}^{-15}}mol/L\] As \[A{{g}_{2}}Cr{{O}_{4}}\] has maximum solubility, it will give maximum \[A{{g}^{+}}\] ions in solution. Hence, it will be used.


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