The thermochemical equation which is associated with ∆H°f, the standard enthalpy of formation, for urea, CO(NH2)2 (s), is:

CO (g) + 2NH3 (g) --> CO(NH2)2 (s) + H2 (g)
CO (g) + 2H2 (g) + N2 (g) --> CO(NH2)2 (s)
C (s) + O (g) + N2 (g) + 2H2 (g) --> CO(NH2)2 (s)
C (s) + 1/2O2 (g) + N2 (g) + 2H2 (g) --> CO(NH2)2 (s)
C (s) + 1/2O2 (g) + 2NH2 (g) --> CO(NH2)2 (s)

Please help

3 answers

You say equation but you have four equations listed. I don't see a question.
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