1. As an acid – It reacts with alkalis to form trioxosulphate (iv) salts.
2NaOH(aq) + SO2(g) → Na2SO3(aq) + H2O(L)
2. As a reducing agent – It reduces oxidizing agents without leaving any traces of sulphur.
2KMnO4(aq) + 5SO2(g) + 2H2O(L) → K2SO4(aq) + 2MnSO4(aq) + 2H2SO4
3. It can combine directly with metallic oxides to form salts.
PbO2(s) + SO2(g) → PbSO4(aq)
NB: 2SO2(s) + SO2(g) → 2SO3(g)
4. As an oxidizing agent –
C(s) + SO2(g) → CO2(s)
NB: SO2 bleaches by reduction unlike chlorine which bleaches by oxidation.