JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2012

  • 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) \[\because \]\[2F(2\times 96500\text{ }C)\] deposits\[Mg=1\text{ }mol\] \[\therefore \] 9.65 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,\[5\times {{10}^{-5}}\]mol of Grignard reagent is obtained.


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