I believe that the balanced chemical equation is:
3H2(g)+N2(g)→2NH3(g), ΔH = -21.9 kcal
We can see that 21.9 kcal of heat is released for every 2
moles of NH3.
The molar mass of NH3 is 17 g/mol, hence:
moles NH3 = 33.68 g / (17 g/mol)
moles NH3 = 1.98 mol
The total energy released is:
total heat = (-21.9 kcal / 2 mol) * 1.98 mol
total heat = -21.70 kcal
