1) Br2 ->HBr -> MgBr2 -> AgBr
Br2 + H2 = 2HBr
2HBr + Mg(OH)2 = MgBr2 + 2H2O
MgBr2 + 2AgNO3 = 2AgBr + Mg(NO3)3
2) S -> H2S -> SO2 -> SO3 -> H2SO4 -> BaSO4
S + H2 = H2S
2H2S + 3O2 = 2SO2 + 2H2O
2SO2 + O2 = 2SO3
SO3 + H2O = H2SO4
H2SO4 + BaCl2 = BaSO4 + 2HCl