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JEE Main & Advanced Chemistry Electrochemistry / विद्युत् रसायन Question Bank Critical Thinking Electrochemistry

  • question_answer
    Aluminium oxide may be electrolysed at 1000°C to furnish aluminium metal (At. Mass = 27 amu; 1 Faraday = 96,500 Coulombs). The cathode reaction is \[A{{l}^{3}}+3{{e}^{-}}\to Al{}^\circ \] To prepare 5.12kg of aluminium metal by this method would require      [AIEEE 2005]

    A)                 \[5.49\times {{10}^{7}}C\] of electricity 

    B)  \[1.83\times {{10}^{7}}C\] of electricity

    C)                 \[5.49\times {{10}^{4}}C\] of electricity

    D)                 \[5.49\times {{10}^{1}}C\] of electricity

    Correct Answer: A

    Solution :

               27 gm of Al is obtained by passing a current of  3 × 96500 C.                     \[\because \]1 gm of Al is obtained by passing a current of \[3\times \frac{96500}{27}C.\]                     \ 5.12 × 103 gm of Al is obtained by passing a current of \[3\times \frac{96500}{27}\times 5.12\times 1000\]                                 = 1.83 × 107 C × 3 = 5.49 × 107C.


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