Given two examples to show that moist `SO_(2)` is a reducing agent.

Explanation

Moist sulphur dioxide reduces `Fe^(3+)` [Iron (III) ] to `Fe^(2+)` [Iron(II)]
`2Fe^(3+)+SO_(2)+2H_(2)OrarrSO_(4)^(2-)+2Fe^(2+)+4H^(+)`
Moist sulphur dioxide decolourises potassium permanganate.
`2MnO_(4)^(-)+5SO_(2)+2H_(2)Orarr5SO_(4)^(2-)+4H^(+)+2Mn^(2+)`