What is the oxidation number of chromium in Cr₂O₇^2- ion? A)+3 B)+12 C)+7 D)+6 E)+14

Question

Quizplus · Accepted Answer

First, we need to determine the total charge of the ion:

1 Cr atom: +x 
12 S atoms: -12 
17 O atoms: -34 
12 P atoms: -24 
1 O atom: -2 
1 S atom: -2

Total charge: -74

Since the whole ion has a charge of -74, the oxidation numbers of all elements must add up to -74.

Thus,

x - 12(2) - 34(-2) - 24(3) - 2 - 2 = -74

Simplifying the equation:

x - 24 + 68 - 72 - 2 - 2 = -74

x - 32 = -74

x = +42

Therefore, the oxidation number of chromium is +6.

The best choice is D (+6) as it is the correct oxidation number calculated using the above method.

What Is the Oxidation Number of Chromium in Cr2O72- Ion