Is there an equation for acid rain? What is it?
S + O2 ==> SO2
SO2 + O2 == SO3 You balance.
S03 + H2O ==> H2SO4.
Many problem I have seen simply say so much S was burned producing so much SO3; therefore, how much H2SO4 will be formed. That is, they ignore the fact that SO2 is an intermediate which must be oxidized further to SO3 before it can become H2SO4. At the same time the "problem" makes the assumption that ALL of the S becomes H2SO4 which probably is never true.
For SO2 + H2O ==> H2SO3 (which is sulfurous acid and not sulfuric acid.). This may be more than you ever wanted to know about acids and acid rain but it's all free.