Exercise 10 | Thermochemistry

Hydrogen (g) reacts with iodine (g) to form hydrogen iodide (g).

Write the chemical equation of this reaction and calculate the ΔH associated.


Data: Hbond (H-H) = 436 kJ.mol-1; Hbond (I-I) = 151 kJ.mol-1; Hbond (H-I) = 297 kJ.mol-1

H(g) + I(g) → 2 HI (g)
 

ΔH = ΣHbond broken - ΣHbond formed

ΔH = ΣHbond (reactants) - ΣHbond (products)

ΔH = Hbond(H-H) + Hbond(I-I) – 2 x Hbond(H-I)

ΔH = -7 kJ.mol-1