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

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

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

Question

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

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

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

| General Chemistry 2

Accepted Answer

H₂(g) + I₂(g) → 2 HI (g)

ΔH = ΣH_{bond broken} - ΣH_{bond formed}

ΔH = ΣH_bond (reactants) - ΣH_bond (products)

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

ΔH = -7 kJ.mol^-1

Exercise 10 | Thermochemistry