Question

bleaching by chlorine water is permanent while bleaching with so2 is temporary

Answer 1

Both sulphur dioxide and chlorine are good bleaching agents. Bleaching action 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.
Sulphour dioxide removes oxygen from the coloured substance and makes it colourless. But atmospheric oxygen slowly takes place of the removed oxygen and because of which the material regains the colour.

Answer 2

Answer:

Both sulphur dioxide and chlorine are good bleaching agents. Bleaching action 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.

Sulphour dioxide removes oxygen from the coloured substance and makes it colourless. But atmospheric oxygen slowly takes place of the removed oxygen and because of which the material regains the colour.