CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2010

  • question_answer
      \[{{E}_{1}},\,{{E}_{2}},{{E}_{3}}\] are the emf values of the three galvanic cells respectively.      
    (i) \[Zn|Zn_{1M}^{2+}||Cu_{0.1M}^{2+}|Cu\]
    (ii) \[Zn|Zn_{1M}^{2+}||Cu_{1M}^{2+}|Cu\]
    (iii) \[Zn|Zn_{0.1\,M}^{2+}||Cu_{1M}^{2+}|Cu\]
          Which one of the following is true?  

    A) \[{{E}_{2}}>{{E}_{3}}>{{E}_{1}}\]              

    B) \[{{E}_{3}}>{{E}_{2}}>{{E}_{1}}\]

    C) \[{{E}_{1}}>{{E}_{2}}>{{E}_{3}}\]                              

    D) \[{{E}_{1}}>{{E}_{3}}>{{E}_{2}}\]

    Correct Answer: B

    Solution :

    For the given cell,                 \[{{E}_{cell}}=E_{cell}^{o}-\frac{0.0591}{2}\log \frac{[Z{{n}^{2+}}]}{[C{{u}^{2+}}]}\] (i)            \[{{E}_{1}}=E_{cell}^{o}-\frac{0.0591}{2}\log \frac{1}{0.1}\]                 \[E_{cell}^{o}-\frac{0.0591}{2}\] (ii) \[{{E}_{2}}=E_{cell}^{o}-\frac{0.0591}{2}\log \frac{1}{1}\]                 \[=E_{cell}^{o}-\frac{0.0591}{2}\times 0\]                 \[=E_{cell}^{o}\] (iii) \[{{E}_{3}}=E_{cell}^{o}-\frac{0.0591}{2}\log \frac{0.1}{1}\]                 \[=E_{cell}^{o}+\frac{0.0591}{2}\] \[\therefore \]                  \[{{E}_{3}}>{{E}_{2}}>{{E}_{1}}\]              


You need to login to perform this action.
You will be redirected in 3 sec spinner