CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2004

  • question_answer
    If three Faradays of electricity is passed through the solutions of\[AgN{{O}_{3}},CuS{{O}_{4}}\]and \[AuC{{l}_{3}},\]the molar ratio of the cations deposited at the cathodes will be:

    A)  \[1:1:1\]                             

    B)  \[1:2:3\]

    C)  \[3:2:1\]             

    D)         \[6:3:2\]

    E)  \[2:3:1\]

    Correct Answer: D

    Solution :

    The increasing order of deposition of cations at the cathode is \[C{{u}^{2+}}<A{{g}^{+}}<A{{u}^{3+}}\]                                 \[E\propto Z\]                 \[A{{g}^{+}}+{{e}^{-}}\xrightarrow[{}]{{}}Ag\]                 \[C{{u}^{2+}}+2{{e}^{-}}\xrightarrow{{}}Cu\]                 \[A{{u}^{3+}}+3{{e}^{-}}\xrightarrow{{}}Au\] 3 Faradays liberate 1 mole of Au, 3 moles of Ag and 3/2 moles of Cu. Thus molar ratio of \[Ag:Cu:Au\text{ }is\text{ }3:3/2:1\text{ }or\text{ }6:3:2\].


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