From the enthalpies of reaction H₂(g) + F₂(g) → 2 HF(g) ΔH = -537 kJ C(s) + 2 F₂(g) → CF₄(g) ΔH = -680 kJ 2 C(s) + 2 H₂(g) → C₂H₄(g) ΔH = +52.3 kJ Calculate H for the reaction of ethylene with F₂: C₂H₄(g) + 6 F₂(g) → 2 CF₄(g) + 4 HF(g)