Why bleaching action of chlorine is permanent but that of so2 is temporary?
Answers
SO2 is a lighter gas and hence it is not permanent it reacts for a temporary time which Cl2 forms a good bonding with CaO and hence it forms CaOCl2 or bleaching powder where a SO2 remains for a shorter period of time and is temporary because of its lighter weight and poor bonding.
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.