NEET AIPMT SOLVED PAPER 2000

  • question_answer
                    \[C{{u}^{+}}(aq)\] is unstable in solution and undergoes simultaneous oxidation and reduction according to the reaction:                 \[2C{{u}^{+}}(aq)C{{u}^{2+}}(aq)+Cu(s)\]                 choose correct \[{{E}^{o}}\] for above reaction if \[E_{C{{u}^{2+}}/Cu}^{0}=0.34\,V\] and \[E_{C{{u}^{2+}}/C{{u}^{+}}}^{0}=0.15\,V\]                          

    A)                 - 0.38 V     

    B)                 + 0.49 V               

    C)                 + 0.38 V 

    D)                 - 0.19 V

    Correct Answer: C

    Solution :

                    From given data  \[(From\,\Delta {{G}^{o}}=-n{{E}^{o}}F)\]                 \[(i)\,Cu(s)\xrightarrow[{}]{{}}C{{u}^{2+}}(aq)+2{{e}^{-}}\]                                                                 \[\Delta G_{1}^{o}=-2\times (-0.34)\times F\]                 \[(ii)\,C{{u}^{2+}}(aq)+{{e}^{-}}\xrightarrow[{}]{{}}C{{u}^{+}}(aq)\]                                                                 \[\Delta G_{2}^{o}=-1\times (0.15)\,\,F\]                 On addition                  \[Cu(s)\xrightarrow[{}]{{}}C{{u}^{2+}}(aq)+{{e}^{-}},\,\,\,\Delta G_{3}^{o}=-1\times {{E}^{o}}\times F\]                 \[\Delta G_{3}^{o}=\Delta G_{1}^{o}+\Delta G_{2}^{o}\]                 \[=(-2\times -0.34\times F)+(-1\times 0.15\times F)\]                 \[=\,+\,0.68\,F-0.15\,F=0.53\,F\]                 \[or\,{{E}^{o}}=-0.53\,V\]                 Reaction \[2C{{u}^{+}}(aq)\rightleftharpoons C{{u}^{2+}}(aq)+Cu(s)\,{{E}^{o}}=?\]                 So,  \[C{{u}^{2+}}(aq)+{{e}^{-}}\rightleftharpoons Cu(s),\,{{E}^{o}}=+0.53\,V\]                 \[\frac{C{{u}^{+}}(aq)C{{u}^{2+}}(aq)+{{e}^{-}};\,\,\,\,{{E}^{o}}=-0.15V}{2C{{u}^{+}}(aq)C{{u}^{2+}}(aq)+Cu(s),\,{{E}^{o}}=+0.38V}\]


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