BCECE Medical BCECE Medical Solved Papers-2001

  • question_answer
    \[Zn(s)+C{{u}^{2+}}(aq)\xrightarrow{{}}Cu(s)+Z{{n}^{2+}}(aq)\] The emf of above reaction is 1.10 V at \[{{25}^{o}}C\]. Find emf of cell well when \[[Z{{n}^{2+}}]=0.1\,M\] \[[C{{u}^{2+}}]=0.1M\]

    A)  1.10 V        

    B)  -1.10 V

    C)  0.110 V        

    D)  -0.110 V

    Correct Answer: A

    Solution :

    Key Idea: Use following relationship to find emf of cell                 \[{{E}_{cell}}={{E}^{o}}-\frac{0.059}{n}\log \frac{[Product]}{[Reactant]}\] Given,   \[{{E}^{o}}=1.10\,\,V\]                 \[[Z{{n}^{2+}}]=0.1\,\,M\]                 \[[C{{u}^{2+}}]=0.1\,\,M\]                 \[{{E}_{cell}}=E_{cell}^{o}-\frac{0.059}{2}\log \left[ \frac{Z{{n}^{2+}}}{C{{u}^{2+}}} \right]\] (\[\because \,\,2\] electrons are involved in cell reaction and concentration of solids is taken as unity) \[\therefore \] \[{{E}_{cell}}=1.10-\frac{0.059}{2}\log \left[ \frac{0.1}{0.1} \right]\] or            \[=1.0-\frac{0.059}{2}\log \,\times 0\]                 \[=1.10-\frac{0.059}{2}\times 0\] \[\therefore \] \[{{E}_{cell}}=1.10\,\,V\]


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