Answer is: B) -50.2 kJ.
Balanced chemical reaction: N₂(g) + 3H₂(g) → 2NH₃(g) ΔH = -100.4 kJ.
This is exothermic reaction, because heat is released and energy is include as product of chemical reaction.
Make proportion, two moles of ammonia released 100.4 kJ of heat, then one mole of ammonia released:
2 mol(NH₃) : (-100.4 kJ) = 1 mol : ΔH.
ΔH = -50.2 kJ; heat released per mole of NH₃.