Question

S - SO2-SO3-Na2SO4-BaSO4

Answer 1

1)S+O2→SO2
2)2SO2+O2→2SO3
3)SO3+H2O→H2SO4 | H2SO4(разб.)+Na→Na2SO4+H2
4) Na2SO4+Ba(OH)2→BaSO4+2NaOH