Which equation corresponds to the bond enthalpy of the H–I bond?

A.     \({\text{HI(g)}} \to \frac{1}{2}{{\text{H}}_{\text{2}}}{\text{(g)}} + \frac{1}{2}{{\text{I}}_{\text{2}}}{\text{(g)}}\)

B.     \({\text{HI(g)}} \to \frac{1}{2}{{\text{H}}_{\text{2}}}{\text{(g)}} + \frac{1}{2}{{\text{I}}_{\text{2}}}{\text{(s)}}\)

C.     \({\text{HI(g)}} \to {{\text{H}}^ + }{\text{(g)}} + {{\text{I}}^ - }{\text{(g)}}\)

D.     \({\text{HI(g)}} \to {\text{H(g)}} + {\text{I(g)}}\)

D

Students found this question to be the most difficult question with only 10.82% correct answers. This was very surprising considering this was a definition question on bond enthalpy which involves the energy needed to break one mole of the bonds to form separated atoms with reactants and products in the gas state.