When potassium dichromate react with Iron sulphite, why its colour change to green?
Answer:
Potassium dichromate, K2Cr2O7, is a crystalline solid with a vivid red-orange color. And, it is an oxidizing agent. So, when mixed with Iron sulfite, FeSO3, which is soluble in water, the sulfite is oxidized to sulfate. This results in Potassium chromium sulfate – and a green color.
Jst to add to the answer above. The colour is due to the different oxidation state of chromium. In potassium dichromate, chromium has oxidation state of 6. When potassium dichromate is reduced ( because it's used to oxidise sulphite) chromium changes from oxidation state 6 to oxidation state 3 in potassium chromium sulfate.
And chromium (III) is green while Chromium (VI) is orange-red
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