Question

What is the oxidation state of chromium in the dichromate ion, `"Cr"_2"O"_7^(2-)`?

Answer 1

+6

Explanation:

Problem: What is the oxidation number (O.N.) of chromium (Cr) in the dichromate ion `"Cr"_2"O"_7"^(2-)`?

Let the O.N. of Cr be `x`. The O.N. of oxygen is -2.

The sum of the oxidation states in an ion must add up to the charge on the ion. The dichromate ion has a charge of `"2"^-`, as indicated by its formula, `"Cr"_2"O"_7"^(2-)`.

`2*x` + `7*`(-2) = (-2)

`2*x` - 14 = -2

Add 14 to both the sides;

`2*x` -14 +14 = -2 +14

`2*x` = 12

Divide both sides by 2 ;

`"2x"/2"` =`"12"/"2"`

`x = 6`

The oxidation number of chromium in the dichromate ion is `+6`.

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