What happens when sulphur dioxide is passed through an aqueous solution of Fe(III) salt?

SO₂ acts as a reducing agent when passed through an aqueous solution containing Fe(III) salt.

It reduces Fe(III) to Fe(II) i.e., ferric ions to ferrous ions.

2Fe³⁺ + SO₂ + 2H₂O ⇒ 2Fe²⁺ + SO₄^2- + 4H⁺