Using Three Equations with Hess’s Law to Calculate

Chapter 3, Problem 9PE

(choose chapter or problem)

Problem 9PE

Using Three Equations with Hess’s Law to Calculate ΔH

Calculate ΔH for the reaction

2 C(s) + H2(g) → C2H2(g)

given the following chemical equations and their respective enthalpy changes:

C2H2(g) + 5/2 O2(g) → 2 CO2(g) + H2O(l) ΔH = -1299.6 kJ

C(s) + O2(g) → CO2(g) ΔH = -393.5 kJ

H2(g) + ½ O2(g) → H2O(l) ΔH = -285.8 kJ

Calculate ΔH for the reaction

NO(g) + O(g)→ NO2(g)

given the following information:

NO(g) + O3(g) → NO2(g) + O2(g) ΔH = -198.9 kJ

O3(g) → 3/2 O2(g) ΔH = -142.3 kJ

O2(g) → 2 O(g) ΔH = 495.0 kJ