J & K CET Medical J & K - CET Medical Solved Paper-2000

  • question_answer
    \[C{{u}^{+}}\]ion is not stable in aqueous solution because of disproportionation reaction.\[{{E}^{o}}\] value for disproportionation of\[C{{u}^{+}}\]is: (Given: \[E_{C{{u}^{2+}}|C{{u}^{+}}}^{o}=0.15V,\]\[E_{C{{u}^{2+}}|Cu}^{o}=0.34\,V\])

    A)  \[-\,0.19V\]                      

    B)  0.38

    C)  0.94V                                   

    D)  \[-\,0.38V\]

    Correct Answer: B

    Solution :

                                \[E_{C{{u}^{2+}}/C{{u}^{+}}}^{o}=0.15\,V\] \[E_{C{{u}^{2+}}/C{{u}^{+}}}^{o}=0.34\,V\] \[C{{u}^{2+}}+{{e}^{-}}\xrightarrow{{}}C{{u}^{+}};\]                        \[{{E}^{o}}=+0.15V\] Or           \[C{{u}^{+}}\xrightarrow{{}}C{{u}^{2+}}+{{e}^{-}};\]        \[E_{1}^{o}=-0.15\,V\] \[\Delta G_{1}^{o}=-nFE_{1}^{o}=-1\times F\times (-0.15)=+0.15\,F\] \[C{{u}^{2+}}+2{{e}^{-}}\xrightarrow{{}}Cu;\]     \[E_{2}^{o}=0.34\,V\] \[C{{u}^{+}}+e\xrightarrow{{}}Cu;\]        \[E_{3}^{o}=?\] \[\Delta G_{2}^{o}=-2\times 0.34\times F\] \[\Delta G_{3}^{o}=-1\times E_{3}^{o}\times F\] \[\Delta G_{3}^{o}=\Delta G_{1}^{o}+\Delta G_{2}^{o}\] \[-E_{3}^{o}F=+0.15F-0.68\,F\] \[E_{3}^{o}=+0.53\,V\] For disproportionation reaction of\[C{{u}^{+}}\]for half-cell reaction: \[C{{u}^{+}}+{{e}^{-}}\xrightarrow{{}}Cu;\]                         \[{{E}^{o}}=+0.53\,V\] \[C{{u}^{+}}\xrightarrow{{}}C{{u}^{2+}}+\overline{e};\]                                \[{{E}^{o}}=-0.15\,V\] \[\therefore \]\[2C{{u}^{2+}}\xrightarrow{{}}C{{u}^{2+}}+Cu;\] \[E_{cell}^{o}=0.38\,V\]


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