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JEE Main & Advanced Sample Paper JEE Main Sample Paper-17

  • question_answer
    A solution containing one mole per litre of each \[Cu{{(N{{O}_{3}})}_{2}};AgN{{O}_{3}};H{{g}_{2}}{{(N{{O}_{3}})}_{2}};Mg{{(N{{O}_{3}})}_{2}}\]is being electrolysed using inert electrodes. The values of standard electrode potentials (reduction potentials in volts are \[Ag/A{{g}^{+}}=0.80\]\[V,2Hg/H{{g}_{2}}^{++}=0.79\,V,\]\[Cu/C{{u}^{++}}=+\,0.24\,V,\,Mg/\]\[M{{g}^{++}}=-2.37\,V.\] With increasing voltage, the sequence of  deposition of metals on the cathode will be

    A)  \[Ag,Hg,Cu\]                    

    B) \[Cu,Hg,Ag\]

    C)  \[Ag,Hg,Cu,Mg\]            

    D)  \[Mg,Cu,Hg,Ag\]

    Correct Answer: A

    Solution :

     Greater the value of standard reduction potential, greater will be its tendency to undergo reduction. So, the sequence of deposition of metals on cathode will be Ag, Hg, Cu. here, magnesium will not be deposited because its standard reduction potential is negative. So, it is strong tandency to undergo oxidation. Therefore, on electrolysis of \[\text{Mg(N}{{\text{O}}_{3}}{{\text{)}}_{2}}\] solution,\[{{\text{H}}_{\text{2}}}\] gas will be evolved at cathode.


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