Redox chemistry of sulfur compounds
Compounds in intermediate oxidation states S(2) or S(4)
can act as both oxidizing and reducing agents
SO2 (g) + Br2 (aq) + 6 H2O ? 2 Br-(aq)+ SO42- (aq) + 4 H3O+ (aq)
can act as a reducing agent . . .
and can act as an oxidizing agent:
SO2 (g) + 2 H2S (g) ? 3 S(s) + 2 H2O
Water is both CATALYST and product ! - autocatalysis
5 SO2 (g) + 2MnO4- (aq) + 6 H2O ? 5SO42- (aq) + 2Mn2+ (aq) + 4 H3O+ (aq)