What is the oxidation number of chromium in the bright orange potassium dichromate (K2Cr2O7)?
Answer and explanation
Correct answer: A. +6 oxidation state
In K2Cr2O7, K is +1 (total +2) and O is -2 (total -14). For neutrality, the two chromium atoms must total +12, giving each Cr an oxidation state of +6. In basic solution, it turns into yellow chromate (CrO4^2-), also Cr(+6).
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