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JEE Main & Advanced JEE Main Paper (Held On 12 April 2014)

  • question_answer
    The \[\left( S{}^\circ  \right)\] of the following substances are: \[C{{H}_{4}}(g)186.2J{{K}^{-1}}mo{{l}^{-1}}\] \[{{O}_{2}}(g)205.2J{{K}^{-1}}mo{{l}^{-1}}\] \[{{H}_{2}}O(g)69.9J{{K}^{-1}}mo{{l}^{-1}}\] The entropy change \[(\Delta {{S}^{o}})\]for the reaction : \[C{{H}_{4}}(g)+2{{O}_{2}}(g)\to C{{O}_{2}}(g)+2{{H}_{2}}O(l)\]is:   [JEE Main Online Paper ( Held On 12 Apirl  2014 )

    A) \[-312.5J{{K}^{-1}}mo{{l}^{-1}}\]

    B) \[-242.8J{{K}^{-1}}mo{{l}^{-1}}\]

    C) \[-108.1J{{K}^{-1}}mo{{l}^{-1}}\]

    D) \[-37.6J{{K}^{-1}}mo{{l}^{-1}}\]

    Correct Answer: B

    Solution :

    \[\Delta {{S}^{o}}={{S}^{o}}_{C{{O}_{2}}}+2\times {{S}^{o}}_{{{H}_{2}}O}-\left( {{S}^{o}}_{C{{H}_{4}}}+2\times S_{{{O}_{2}}}^{o} \right)\] \[=(213.6+2\times 69.9)(186.2+2\times 205.2)\] \[=-242.8J{{K}^{-1}}mo{{l}^{-1}}.\]


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