Question

What is the oxidation state for the ion Cr2O7^2-?

Answer 1

Oxygen `-2` and Chromium `+6`

Explanation:

The oxidation state of oxygen is always `-2` except in `H_2O_2` it is `-1` and in `OF_2` it is `+2`.

So the oxidation state of oxygen in `Cr_2O_7^(2-)` is `color(red)(-2)`. Assume that `x` is the oxidation state of `Cr` in `Cr_2O_7^(2-)`, then to find `x`:

`(2xxx)+4xx(-2)=-2=> x-8=-2=>x=+6`

Therefore, the oxidation state of `Cr` in `Cr_2O_7^(2-)` is `color(blue)(+6)`.