J & K CET Medical J & K - CET Medical Solved Paper-2001

  • question_answer
    If the enthalpy change for the reaction is\[2N{{H}_{3}}(g)\xrightarrow{{}}{{N}_{2}}(g)+3{{H}_{2}}(g)\]is\[92\,kJ\,mo{{l}^{-1}}\] the enthalpy of formation of ammonia is:

    A) \[-23.0\text{ }kJ\text{ }mo{{l}^{-1}}\]    

    B)  \[-46\text{ }kJ\text{ }mo{{l}^{-1}}\]

    C) \[-92.0\text{ }kJ\text{ }mo{{l}^{-1}}\]    

    D) \[46\text{ }kJ\text{ }mo{{l}^{-1}}\]

    Correct Answer: B

    Solution :

                    \[2N{{H}_{3}}(g)\xrightarrow{{}}{{N}_{2}}(g)+3{{H}_{2}}(g);\] \[\Delta H=+92\,kJ\] \[{{N}_{2}}(g)+3{{H}_{2}}(g)\xrightarrow{{}}2N{{H}_{3}}(g);\]                                                 \[\Delta H=-92\,kJ\] \[\frac{1}{2}{{N}_{2}}(g)+\frac{3}{2}{{H}_{2}}(g)\xrightarrow{{}}N{{H}_{3}}(g);\]                                                 \[\Delta H=-\,46\,kJ\] Hence, enthalpy of formation of\[N{{H}_{3}}\] is \[-\text{ }46\text{ }kJ\] \[mo{{l}^{-1}}\].


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