## Chemistry: The Central Science (13th Edition)

$S(s) + \frac{3}{2}O_2(g) --> SO_3(g)$ $\Delta H ^o _f (SO_3(g))= -395.2 kJ/mol$
1. Write the unbalanced equation: $S(s) + O_2(g) --> SO_3(g)$ 2. Balance it: $S(s) + \frac{3}{2}O_2(g) --> SO_3(g)$ 3. The $\Delta H^o$ values can be founded in the book's final pages. $\Delta H ^o _f (SO_3(g))= -395.2 kJ/mol$