WB JEE Medical WB JEE Medical Solved Paper-2015

  • question_answer
    At temperature of 298K, the emf of the following electrochemical cell, Ag \[(s)\,A{{g}^{+}}(0.1M)||Z{{n}^{2+}}(0.1M)|Zn(s)\]will be (Given\[{{E}^{o}}_{cell}=-1.562\,\text{V}\])

    A) \[-1.532V\]            

    B) \[-1.503V\]                      

    C) \[1.532V\]            

    D) \[-3.06V\]                     

    Correct Answer: A

    Solution :

     From the given cell, the cell reaction is \[2Ag(s)+Z{{n}^{2+}}(0.1\,M)\xrightarrow{{}}\] \[2A{{g}^{+}}(0.1\,M)+Zn(s)\] The Nernst equation is \[{{E}_{cell}}={{E}^{o}}_{cell}-\frac{0.0591}{n}\log \frac{{{[A{{g}^{+}}]}^{2}}}{[Z{{n}^{2+}}]}\] or,  \[{{E}_{cell}}=(-1.562)-\frac{(0.0591)}{2}\log \frac{{{(0.1)}^{2}}}{(0.1)}\]  (where, \[{{E}^{o}}_{cell}=-1.562\,V\]) or  \[{{E}_{cell}}=(-1.562)-\frac{0.0591}{2}\log {{10}^{-1}}\] \[=-1.562+\frac{0.0591}{2}\] \[=-1.562+0.02955=-1.532\,\text{V}\]


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