CET Karnataka Engineering CET - Karnataka Engineering 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 :

    \[MgC{{l}_{2}}\xrightarrow{{}}M{{g}^{2+}}+2C{{l}^{-}}\] \[M{{g}^{2+}}+\underset{2\,\,F}{\mathop{2{{e}^{-}}}}\,\xrightarrow{{}}\underset{1\,\,mol}{\mathop{Mg}}\,\] (at cathode) \[\because \,\,2F(2\times 96500\,C)\] deposits \[Mg=1\,\,mol\] \[\therefore \,\,9.65\,C\] charge will deposit \[Mg=\frac{1\times 9.65}{2\times 96500}\] 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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