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JCECE Medical JCECE Medical Solved Paper-2004

  • question_answer
    The heat of formation of \[\text{MgO,A}{{\text{l}}_{\text{2}}}{{\text{O}}_{\text{3}}}\]and \[\text{Si}{{\text{O}}_{2}}\]are \[-692,\,-1676,-911,\,\text{kJ}\text{mo}{{\text{l}}^{-1}}.\] 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, \[MgO,\Delta {{H}_{f}}=-692\,\text{kJ}\,\text{mo}{{\text{l}}^{-1}}\] \[Si{{O}_{2}},\Delta {{H}_{f}}=-911\,\text{kJ}\,\text{mo}{{\text{l}}^{-1}}\] \[A{{l}_{2}}{{O}_{3}},\Delta {{H}_{f}}=-1676\,\text{kJ}\,\,\text{mo}{{\text{l}}^{-1}}\] \[\therefore \]MgO is most stable oxide among given choices.


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