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Dichromate has an overall charge of -2. We know oxygen has a -2 charge and, with

ID: 498261 • Letter: D

Question

Dichromate has an overall charge of -2. We know oxygen has a -2 charge and, with 7 oxygen atoms present, contributes a charge of -14. This means we need +12 to reach a net charge of -2. There are 2 Cr present so each has an oxidation state of 6+. The cr on the product side is cr^3+. Now looking at the ethyl alcohol... the overall charge is 0. Each H contributes +1, and the o contributes 2- The 4- difference is split over two carbons results in an oxidation state of 2-. The oxidation state of carbon in carbon dioxide is 4+. Practice this calculation. Did you arrive at 4+?

Explanation / Answer

CH3 CH2OH = 0

2C + 6H + 1O = 0

or, 2C + 6 * +1 + 1*-2 = 0

or, 2C = +2 - 6

or, C = -2

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CO2 = 0

1*C + 2* O = 0

or, 1*C + 2*-2 = 0

or, C -4 = 0

or, C = +4