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Question
When orange solution containing \[\ce{Cr2O^{2-}7}\] ion is treated with an alkali, a yellow solution is formed and when \[\ce{H^+}\] ions are added to yellow solution, an orange solution is obtained. Explain why does this happen?
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Solution
This is due to the interconversion of dichromate (orange) to chromate ion (yellow).
\[\ce{\underset{\underset{(Orange)}{Dichromate}}{Cr2O^{2-}7} ⇌[OH^-][H^+] \underset{\underset{(Yellow)}{Chromate}}{CrO^{2-}4}}\]
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