Use Hess's Law to determine ΔH° for the conversion of methane to ethylene: 2 CH₄ (g) → C₂H₄ (g) + 2 H₂ (g), by manipulating and combining the following equations:
- C₂H₄ (g) + H₂ (g) → C₂H₆ (g) ∆H°= -285.8 kJ
- H₂ (g) + 1/2 O₂ (g) → H₂O (l) ∆H° = -285.8 kJ
- CH₄ (g) + 2 O₂ (g) → CO₂ (g) + 2 H₂O (l) ∆H°= - 890.3 kJ
- 2 C₂H₆ (g) + 7 O₂ (g) → 4 CO₂ (g) + 6 H₂O (l) ∆H°= -3120.8 kJ