Chapter 5, Problem 51PS

Enthalpy changes for the following reactions can be determined experimentally:

N₂(g) + 3 H₂(g) → 2 NH₃(g)

Δ_rH° = –91.8 kJ/mol-rxn

4 NH₃(g) + 5 O₂(g) → 4 NO(g) + 6 H₂O(g)

Δ_rH° = –906.2 kJ/mol-rxn

H₂(g) + ½ O₂(g) → H₂O(g)

Δ_rH° = –241.8 kl/mol-rxn

Use these values to determine the enthalpy change for the formation of NO(g) from the elements (an enthalpy change that cannot be measured directly because the reaction is reactant-favored).

½ N₂(g) + ½ O₂(g) → NO(g) Δ_rH° = ?