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NEET Sample Paper NEET Sample Test Paper-88

  • question_answer
    The enthalpies of the following reactions are shown below. \[\frac{1}{2}{{H}_{2}}(g)+\frac{1}{2}{{O}_{2}}(g)\to OH(g);\] \[\Delta H=42.09\,kJ\,mo{{l}^{-1}}\] \[{{H}_{2}}(g)\to 2H(g);\]\[\Delta H=435.89\,kJ\,mo{{l}^{-1}}\] \[{{O}_{2}}(g)\to 2O(g);\]\[\Delta H=495.05\,kJ\,mo{{l}^{-1}}\] Calculate the \[O-H\] bond energy for the hydroxyl radical.

    A) \[223.18\,kJ\,mo{{l}^{-1}}\]

    B)        \[423.38\,kJ\,mo{{l}^{-1}}\]

    C) \[513.28\,kJ\,mo{{l}^{-1}}\]

    D)        \[113.38\,kJ\,mo{{l}^{-1}}\]

    Correct Answer: B

    Solution :

    [b] We have to calculate the enthalpy of the reaction \[OH\,(g)\to O\,(g)+H\,(g)\] From the given reactions, this can be obtained as follows. \[-\left[ \frac{1}{2}{{H}_{2}}(g)+\frac{1}{2}{{O}_{2}}(g)\to OH(g) \right];\]\[\Delta H=-42.09\,kJ\,\,mo{{l}^{-1}}\] \[+\frac{1}{2}[{{H}_{2}}(g)\to 2H(g)];\]\[\Delta H=\frac{1}{2}\times 435.89\,kJ\,\,mo{{l}^{-1}}\] \[+\frac{1}{2}[{{O}_{2}}(g)\to 2O(g)];\]\[\Delta H=\frac{1}{2}\times 495.05\,kJ\,\,mo{{l}^{-1}}\] Add \[\overset{{}}{\mathop{\overline{OH(g)\to H(g)+O(g)}}}\,\,\,\,;\]\[\Delta H=\]\[\overline{423.38\,\,kJ\,\,mo{{l}^{-1}}}\]


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