BHU PMT BHU PMT (Mains) Solved Paper-2010

  • question_answer
    The standard reduction potentials of Ag, Cu, Co and Zn are 0.799, 0.337, -0.277, -0.762 V respectively. Which of the following cells will have maximum cell emf?

    A) \[Zn|Z{{n}^{2+}}(1M)||C{{u}^{2+}}(1M)|Cu\]

    B) \[Zn|Z{{n}^{2+}}(1M)||A{{g}^{+}}(1M)|Ag\]

    C)  \[Cu|C{{u}^{2+}}(1M)||A{{g}^{+}}(1M)|Ag\]

    D) \[Zn|Z{{n}^{2+}}(1M)||C{{o}^{2+}}(1M)|Co\]

    Correct Answer: B

    Solution :

                     \[{{E}_{cell}}=E_{cell}^{o}-\frac{0.0591}{n}\log \frac{[oxidised\,species]}{[reduced\text{ }species]}\] Since, concentration of all the ions is equal, higher the value of\[E_{cell}^{o},\]higher is the\[{{E}_{cell}}\]  \[E_{cell}^{o}={{E}_{cathode}}-{{E}_{anode}}\]                 \[=0.337-(-0.762)=1.09\]  \[E_{cell}^{o}=0.799-(-0.762)=1.56V\]  \[E_{cell}^{o}=0.799-0.337=0.46\,V\]  \[E_{cell}^{o}=-0.227-(-0.762)=0.53\,V\] Thus, emf is maximum for the cell given in option .


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