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KVPY Sample Paper KVPY Stream-SX Model Paper-28

  • question_answer
    Zn Amalgam is prepared by electrolysis of aqueous \[ZnC{{l}_{2}}\] using Hg cathode (9gm). How much current is to be passed through \[ZnC{{l}_{2}}\] solution for 1000 second to prepare a Zn Amalgam with 25 % Zn by wt. (Zn = 65.4)                  

    A) 5.6 amp

    B) 7.2 amp     

    C) 8.85 amp

    D) 11.2 amp    

    Correct Answer: C

    Solution :

    Let x gm of Zn deposit on 9 gm of Hg % of Zn in Amalgam\[=\frac{{{m}_{zn}}\times 100}{{{m}_{zn}}\times {{m}_{Hg}}}\]
    \[=\frac{x}{9+x}=100=25\]
    \[\therefore x=3gm\]
    \[Eq.\,\,of\,\,Zn=\frac{3\times 2}{65.4}\]
    \[\frac{{}^{n}{{Z}_{n}}}{1}=\frac{{{n}_{{{e}^{-}}}}}{2}=\frac{Q}{2f}=\frac{it}{2f}\]
    Current =\[\,i=\frac{6}{65.4}\times \frac{96500}{1000}=8.85amp.\]


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