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JEE Main & Advanced Chemistry Electrochemistry / विद्युत् रसायन Question Bank Electrode potential Ecell Nernst equation and ECS

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    Aluminium displaces hydrogen from dilute HCl whereas silver does not. The e.m.f. of a cell prepared by combining \[Al/A{{l}^{3+}}\] and \[Ag/A{{g}^{+}}\]is  2.46 V. The reduction potential of silver electrode is \[+0.80\ V\]. The reduction potential of aluminium electrode is    [KCET  2004]

    A)                 \[+1.66\ V\]       

    B)                 \[-3.26\,V\]

    C)                 \[3.26\ V\]         

    D)                 \[-1.66\ V\]

    Correct Answer: D

    Solution :

               Al displaces H from  HCl but silver cannot it means Al is situated above the Ag in ECS, hence Al will acts as anode and Ag will act as cathode.                    \[E_{Cell}^{0}=E_{Cathode}^{0}-E_{Anode}^{0}\] \[=E_{A{{g}^{+}}/Ag}^{0}-E_{A{{l}^{3+}}/Al}^{0}\]                                 \[2.46=0.8-E_{A{{l}^{3+}}/Al}^{0}\]; \[E_{Al}^{0}=0.8-2.46=-1.66\ V\].


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