Use bond enthalpies to estimate ∆Hrxn for the Haber process below in which nitrogen from the air is ‘fixed’ into a usable form. Compare this with ∆Hrxn calculated from ∆Hºf , which is –46.19 kJ per mol of NH₃(g). If there is a difference, why is there a difference? Which do you expect to be more accurate and why?

N₂(g) + 3H₂(g) → 2NH₃(g)