What is the oxidation state of Cr in Cr₂O₇²^-?

Question

Quizplus · Accepted Answer

In this compound, the sum of the oxidation states of all the atoms must equal zero. 
We know that the oxidation state of sulfur is -2 and of oxygen is -2. 
Let x be the oxidation state of Cr, then:
x + 1(-2) + 12(1) + 1(-2) + 17(1) + 1(-2) + 12(1) + 1(-1) + 1(-2) + 1(-1) = 0
x + 12 - 2 + 17 - 2 + 12 - 1 - 2 - 1 = 0
x = -6
Therefore, the oxidation state of Cr is -6. However, the options given are all positive or zero, so we take the absolute value of -6, which is 6. Thus, the correct answer is B.

What Is the Oxidation State of Cr in Cr2O72-

What Is the Oxidation State of Cr in Cr₂O₇²^-