The oxidation number of Cr in Cr₂O₇ ^2-is: A)+2. B)-2. C)+7. D)+6. E)none of the above

Question

Quizplus · Accepted Answer

In the given compound, the oxidation number of Sulfur is -2. Oxygen has an oxidation number of -2, which means the total oxidation number contributed by sulfur and oxygen is -18. 
Overall charge of the compound is -12. Therefore, the sum of oxidation numbers of Chromium and Sulfur should cancel out the negative charge.
Let the oxidation number of Chromium be "x".
x + (-2) + (-12) = -12
x = +2
Therefore, the oxidation state of Chromium is +2 or +6. But since the options only have +2 and +6, the answer is D.

The Oxidation Number of Cr in Cr2O7 2- is

The Oxidation Number of Cr in Cr₂O₇ ^2-is