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NEET Sample Paper NEET Sample Test Paper-25

  • question_answer
    Standard free energies of formation (in kJ/mol) at 298 K are -237.2, -394.4 and -8.2 for \[{{H}_{2}}O(l),C{{O}_{2}}(g)\]and pentane (g), respectively. The value of \[E_{cell}^{o}\]for the pentane-oxygen fuel cell is

    A)  2.0968 V                     

    B)  1.0968 V

    C)  0.0968 V                     

    D)  1.968 V

    Correct Answer: B

    Solution :

     \[{{C}_{5}}{{H}_{12}}+8{{O}_{2}}\xrightarrow{{}}5C{{O}_{2}}+6{{H}_{2}}O\] \[\Delta {{G}^{o}}=5\times {{G}^{o}}C{{O}_{2}}+6\times {{G}^{o}}{{H}_{2}}O-G_{{{C}_{5}}{{H}_{12}}}^{o}-8\times G_{{{O}_{2}}}^{o}\] \[=5\times (-394.4)+6\times (-237.2)+8.2\] \[=-3387\,kJ\] \[\Delta {{G}^{o}}=nF{{E}^{o}}\] \[-3387\times {{10}^{3}}=32\times {{E}^{o}}\times 96500\] \[[{{({{C}^{-2.4}})}_{5}}\xrightarrow{{}}5({{C}^{4+}})+32e]\] \[\therefore \]\[{{E}^{o}}=1.0968\,V;n=32\]


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