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JEE Main & Advanced Chemistry Thermodynamics / रासायनिक उष्मागतिकी Question Bank Topic Test - Thermodynamics and Thermochemistry (8-5-21)

  • question_answer
    Values of heats of formation for \[Si{{O}_{2}}\]and \[MgO\] are \[-48.4\] and \[-34.7\,kJ\] respectively. The heat of the reaction \[2Mg+Si{{O}_{2}}\to 2MgO+Si\] is

    A) \[21.16\,kJ\]

    B) \[-21.10\,kJ\]

    C) \[-13.62\,kJ\]

    D) \[13.6\,kJ\]

    Correct Answer: B

    Solution :

    [b] \[\Delta {{H}_{(\text{reaction})}}=2\Delta H_{f}^{0}\,(MgO)=-\Delta H_{f}^{0}\,(Si{{O}_{2}})\]                        \[=2\,(-\,34.7)-(-\,48.4)=-21\,kJ.\]


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