S + O2 → SO2 SO2 + H2O → H2SO3 H2SO3 + H2O → H2SO4 H2SO4 can also be used to represent H2SO3 + O2 → H2SO4
S + O2 → SO2
SO2 + H2O → H2SO3
H2SO3 + H2O → H2SO4
H2SO4 can also be used to represent H2SO3 + O2 → H2SO4