Question

S-->H2S-->SO2-->X-->H2SO4-->X

Answer 1

S + H2 -> H2S
2H2S + 3O2 -> 2SO2 + 2H2O
2SO2 + O2 -> 2SO3
SO3 + H2O -> H2SO4
H2SO4 + CaO -> CaSO4 + H2O