CET Karnataka Medical CET - Karnataka Medical Solved Paper-2010

  • question_answer
    9.65 C of electric current is passed through fused anhydrous magnesium chloride. The magnesium  metal  thus,  obtained  is completely converted into a Grignard reagent. The number of moles of the Grignard reagent obtained is

    A)  \[5\times {{10}^{-4}}\]

    B)  \[1\times {{10}^{-4}}\]

    C)  \[5\times {{10}^{-5}}\]        

    D)  \[1\times {{10}^{-5}}\]

    Correct Answer: C

    Solution :

    \[MgC{{l}_{2}}\xrightarrow{{}}M{{g}^{2+}}+2C{{l}^{-}}\] \[M{{g}^{2+}}+\underset{2F}{\mathop{2{{e}^{-}}}}\,\xrightarrow{{}}\underset{1\,mol}{\mathop{Mg}}\,\] (at cathode) \[\because \] \[2F(2\times 96500C)\] deposits \[Mg=1\text{ }mol\] \[\therefore \]  \[9.65\text{ }C\]charge will deposit \[Mg=\frac{1\times 9.65}{2\times 96500}\] \[=5\times {{10}^{-5}}mol\] In order to prepare Grignard reagent, one mole of \[Mg\] is used per mole of reagent obtained. Thus, by \[5\times {{10}^{-5}}mol\,\,Mg,\] \[5\times {{10}^{-5}}\] mole of Grignard reagent are obtained.


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