What is difference between bleaching action of SO2 and Cl2 gas.

What is difference between bleaching action of SO₂ and Cl₂ gas.

Ans. SO₂ gas is presence of water gives nascent hydrogen. Nascent hydrogen decolourised  the coloured substance once. i.e., bleaching action of SO₂ is a reducing action.

                   SO₂ + 2H₂O → H₂SO₄+2[H]

                   Colour substance  + [H] → Colourless substance

                   Colour substance + [O] → Colourless Substance