Addition of chlorine to potassium iodide solution gives it a dark violet colour but excess chlorine makes it colourless.explain

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Solution

A test tube contains a layer of potassium iodide solution over a denser layer of carbon tetrachloride. Chlorine is bubbled through the potassium iodide layer. The chlorine reacts with the iodide to form iodine. In the aqueous layer the brown triiodide ion is formed by the reaction of iodine with iodide. In the carbon tetrachloride layer, iodine forms a violet solution. The iodine in the aqueous layer reacts further with chlorine to form iodine monochloride. As more chlorine is added, the iodine reacts with the excess chlorine to form iodine trichloride and the solution decolorizes. Some iodine remains in the carbon tetrachloride layer.

This demonstration illustrates that chlorine is a stronger oxidizing agent than iodine, since iodide is oxidized by chlorine to iodine.

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