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JCECE Engineering JCECE Engineering Solved Paper-2004

  • question_answer
    The heat of formation of \[MgO,\,\,A{{l}_{2}}O\] and \[Si{{O}_{2}}\] are \[-692,\,\,\,-1676,\,\,\,-911,\,\,\,kJ\,\,mo{{l}^{-1}}\]. Most stable oxide is:

    A) \[MgO\]

    B) \[A{{l}_{2}}{{O}_{3}}\]

    C) \[Si{{O}_{2}}\]

    D)  cannot be predicted

    Correct Answer: A

    Solution :

    Key Idea: Greater the amount of given out as heat of formation more will be stability of oxide. Given,   \[MgO,\,\,\Delta {{H}_{f}}=692\,\,kJ\,\,mo{{l}^{-1}}\]                 \[Si{{O}_{2}},\,\,\Delta {{H}_{f}}=-911\,\,kJ\,\,mo{{l}^{-1}}\]                 \[A{{l}_{2}}{{O}_{3}},\,\,\Delta {{H}_{f}}=-1676\,\,kJ\,\,mo{{l}^{-1}}\] \[\therefore \]\[MgO\] is most stable oxide among given choices.


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