Question

Bleaching of flowers by chlorine is permanent while that by sulphur dioxide is temporary why

Answer 1

Both sulphur dioxide and chlorine are good bleaching agents. Bleachingaction of chlorine is based on oxidation while that of sulphur is based on reduction. Chlorine acts with water to produce nascent oxygen. This oxygen combines with colourd substance and makes it colourless.

Answer 2

Hey !!

Cl₂ bleaches coloured material by oxidation

     Cl₂ + H₂O ------> 2HCl + O

Coloured Material + [O] -----> Colourless

Hence, bleaching is permanent.

In contrast, SO₂ bleaches coloured material by reduction and hence bleaching is temporary since when the bleached colourless material is exposed to air, it gets oxidised and the colour is restored.

    SO₂ + 2H₂O -----> H₂SO₄ + 2H

Coloured Material + H -----> Colourless material --(aerial)--> Colourless material

Oxidation........!!

Good luck !!