chem勁人入黎

As follows:

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2008-01-15 13:46:16 補充：
Sorry that I have missed out a point. Halogens refer to all Group VIl elements and they will undergo redox reaction with sulphite ions. They turn colourless whenever they are reduced by suphite ions.

2008-01-15 13:52:02 補充：
The below one has missed out that redox reaction consists of both oxidation and reduction, as I have mentioned above. By looking at the equation, you will know how come sodium sulphite turns halogens to colourless.

Reaction of halogen with sodium sulphite is redox reaction.

sulphite ions is a reducing agent while halogen is oxidizing agent.

halogen can be reduced to halide ions by sulphite ions while sulphite ions can be oxidized to sulphate ions by halogen.

PS：since the oxidation state of sulphite ions is quite low, so it always is a reducing agent.

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