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JEE Main & Advanced Sample Paper JEE Main Sample Paper-42

  • question_answer
    \[\Delta {{S}^{o}},\]change in entropy for the following cell reaction is \[2{{H}_{2}}+{{O}_{2}}\to 2{{H}_{2}}O\](Given :\[{{E}^{o}}_{cell}=1.23V,\] \[\Delta H_{f}^{o}({{H}_{2}}O)=-285.8\,\text{kJ}\,\text{mo}{{\text{l}}^{-1}}\],\[\Delta {{G}^{o}}=-\,474.78\text{kJ}\,)\]

    A) \[-126.7\text{J}{{\text{K}}^{-1}}\]            

    B) \[+126.7\,\text{J}{{\text{K}}^{-1}}\]

    C) \[-324.9\,\text{J}{{\text{K}}^{-1}}\]                      

    D) \[324.9\,\text{J}{{\text{K}}^{-1}}\]

    Correct Answer: C

    Solution :

    \[\Delta {{G}^{o}}=\Delta {{H}^{o}}-T\Delta {{S}^{o}}\] \[\Delta {{H}^{o}}=2\times \Delta H_{f}^{o}\] \[=-571.6\,\text{kJ/mol}\] \[-474.78=-571.6-298\times \Delta {{S}^{o}}\] \[\Delta {{S}^{o}}=-324.9J{{K}^{-1}}\]


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