What is the oxidation state of chromium in the potassium dichromate compound (K₂Cr₂O₇)?
Answer and explanation
Correct answer: D. +6
- Step 1: Assign known oxidation numbers: K = +1, O = -2. Step 2. The sum of oxidation numbers in a neutral compound is zero: 2(+1) + 2(Cr) + 7(-2) = 0. Step 3. 2 + 2(Cr) - 14 = 0 => 2(Cr) - 12 = 0 => 2(Cr) = +12 => Cr = +6. Answer: +6. Why not the others: +3 is the reduced form (Cr³⁺); +7 is the oxidation state of Mn in KMnO₄; +4 is CrO₂.
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