In the conversion of CrO₄^-2 → Cr₂O₇^2-, the oxidation number of oxygen

Explanation:

In the conversion of CrO₄²⁻ (chromate ion) to Cr₂O₇²⁻ (dichromate ion), the oxidation state of chromium changes, but the oxidation number of oxygen remains the same.

In both the chromate and dichromate ions, oxygen is bonded to chromium in the form of oxide (O²⁻), where the oxidation state of oxygen is -2. So, during the conversion from CrO₄²⁻ to Cr₂O₇²⁻, the oxygen atoms retain their oxidation number of -2.

Final Answer

The correct answer is remains unchanged.