Question

Which one following molecule will have different value of molar enthalpy of formation, one calculate using bond energy concept and other measured calorimetrically
1) C2H6
2) but-1,3-diene
3) 1, 4-cyclohexadiene
4) N2O

Answer 1

1) C₂H₆ H =-84.67 kj/mol H<0
2) but-1,3-diene H<0
3) 1, 4-cyclohexadiene H<0
Right answer 4) N2O. N₂O has molar enthalpy of formation H=81.55 kj/mol H>0