NEET NEET SOLVED PAPER 2013

  • question_answer
    A button cell used in watches functions as following
    \[Zn(s)+A{{g}_{2}}O(s)+{{H}_{2}}O(l)2Ag(s)\] \[+Z{{n}^{2+}}(aq)+2O{{H}^{-}}(aq)\]
    If half-cell potentials are
    \[Z{{n}^{2+}}(aq)+2{{e}^{-}}\to Zn(s){{E}^{o}}=-0.76V\]
    \[A{{g}_{2}}O(s)+{{H}_{2}}O(l)+2{{e}^{-}}\] \[\to 2Ag(s)+2O{{H}^{-}}(aq),\]\[{{E}^{o}}=0.34V\]
    The cell potential will be

    A)  1.10 V

    B)  0, 42 V

    C)  0.84 V 

    D)  1.34 V

    Correct Answer: A

    Solution :

    Anode is always the site of oxidation thus anode half-cell is \[Z{{n}^{2+}}(aq)+2{{e}^{-}}\xrightarrow[{}]{{}}Zn(s);{{E}^{o}}=-0.76\,V\] Cathode half-cell is \[A{{g}_{2}}O(s)+{{H}_{2}}O(l)+2{{e}^{-}}\xrightarrow[{}]{{}}\] \[2Ag(s)+2O{{H}^{-}}(ag);{{E}^{o}}=0.34\,V\] \[{{E}^{o}}_{cell}={{E}^{o}}_{cathode}-{{E}^{o}}_{anode}\] \[=0.34-(-0.76)=+1.10\,\,V\]


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