For the following reactions, the ΔH° rxn is not equal to ΔH° f for the product except for ________.
a. H₂O (l) + 1/2 O₂ (g) → H₂O₂(l)
b. N₂ (g) + O₂ (g) → 2NO (g)
c. 2H₂ (g) + O₂ (g) → 2H₂O (g)
d. 2H₂ (g) + O₂ (g) → 2H₂O (l)
e. 2C(s, graphite) + 2H₂(g) → C₂H₄ (g)