question_answer

Which of the reaction defines \[\Delta H_{f}^{o}\] [IIT -JEE (Screening) 2003]

A)                 \[{{C}_{(\text{diamond})}}+{{O}_{2}}(g)\,\to \,C{{O}_{2}}(g)\]

B)                 \[\frac{1}{2}{{H}_{2}}(g)+\frac{1}{2}{{F}_{2}}(g)\,\to \,HF(g)\]

C)                 \[{{N}_{2}}(g)+3{{H}_{2}}(g)\,\to \,2N{{H}_{3}}(g)\]

D)                 \[CO(g)+\frac{1}{2}{{O}_{2}}(g)\,\to \,C{{O}_{2}}(g)\]