ChemistryOxidation and reductionWAEC
What is the oxidation number of chromium in potassium heptaoxodichromate(VI), K₂Cr₂O₇?
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Answer: C. +6
2(+1) + 2Cr + 7(−2) = 0 gives 2Cr = +12, so each Cr is +6, as the name shows.
An AdmitMe practice question, written for the WAEC syllabus. Not an official past question.