Question

Which of the reaction defines $\Delta H_f^0$?
(a) $C_{(diamond)}+O_2(g) \longrightarrow CO_2(g)$(b) $\frac{1}{2} H_{2(g)} + \frac{1}{2} F_{2(g)} \longrightarrow HF_{(g)}$
(c) $N_2_{(g)} + 3H_2_{(g)} \longrightarrow 2NH_3_{(g)}$(d) $CO_{(g)} + \frac{1}{2} O_{2(g)} \longrightarrow CO_{2(g)}$

Answer 1

a) is the correct answer