Nitrogen and hydrogen combine to form ammonia in the Haber process. Calculate (in kJ) the standard enthalpy change ΔH° for the reaction written below, using the bond energies given. N₂(g) + 3H₂(g) → 2NH₃(g)
Bond: N≡N H-H N-H
Bond energy(kJ/mol) : 945 432 391

Question

Quizplus · Accepted Answer

The standard enthalpy change ΔH° can be calculated using the bond energies: ΔH° = Σ(Bond energies of reactants) - Σ(Bond energies of products). For the reaction: ΔH° = [(1 x 945) + (3 x 432)] - [(6 x 391)] = 2241 - 2346 = -105 kJ.

Nitrogen and Hydrogen Combine to Form Ammonia in the Haber