RAJASTHAN PMT Rajasthan - PMT Solved Paper-2007

  • question_answer
    Find out emf of cell, \[Zn;Z{{n}^{2+}}(1M)|\,|\,\,C{{u}^{2+}}(1M);\,\,Cu\,\,E{}^\circ \]for \[Z{{n}^{2+}}/Zn=-0.76;\,\,E{}^\circ for\,\,C{{u}^{2+}}/Cu=+0.34\]

    A) \[+1.10\,\,V\]                   

    B)        \[-1.10\,\,V\]

    C)        \[-0.76\]                              

    D)        \[-0.42\]

    Correct Answer: A

    Solution :

    \[E_{cell}^{\text{o}}=E_{cathode}^{\text{o}}-E_{anode}^{\text{o}}\] Oxidation half reaction\[=Zn\xrightarrow{{}}Z{{n}^{2+}}2{{e}^{-}}\] \[\frac{\operatorname{Re}duction\,\,half\,\,reaction=C{{u}^{2+}}+2{{e}^{-}}\xrightarrow{{}}Cu}{Cell\,\,reaction=Zn+C{{u}^{2+}}\xrightarrow{{}}2Z{{n}^{2+}}+Cu}\]                \[E_{right}^{\text{o}}-E_{left}^{\text{o}}=E_{cell}^{\text{o}}\]                 \[=0.34-(-0.76)\]                 \[=0.34+0.76\]                 \[=+1.10\,\,V\]


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