For which of the following reactions does the heat of reaction (ΔH⁰ rxn) equal the heat of formation ( ΔH⁰ f) for the product?
[Select all that apply.]
a. 2C (graphite) + 2H₂ (g) → C₂H₄ (g)
b. H₂ (g) + 12O₂ (g) → H₂O (l)
c. CaO (s) + CO₂ (g) → CaCO₃ (s)
d. Mg (s) + Cl₂ (g) → MgCl₂ (s)
e. 4C (graphite) + 6H₂ (g) + O₂ (g) → 2C₂H₆O (l)
f. N₂(s) + O₃ (g) → N₂O₃ (g)