The difference in oxidation state of chromium in chromate and dichromate salts is ______

We need to find the difference in oxidation state of chromium in chromate (CrO$$_4^{2-}$$) and dichromate (Cr$$_2$$O$$_7^{2-}$$) salts. Let the oxidation state of Cr in chromate be $$x$$.

$$ x + 4(-2) = -2 $$

$$ x - 8 = -2 $$

$$ x = +6 $$

Let the oxidation state of Cr in dichromate be $$y$$.

$$ 2y + 7(-2) = -2 $$

$$ 2y - 14 = -2 $$

$$ 2y = 12 $$

$$ y = +6 $$

The difference in oxidation states:

$$ x - y = +6 - (+6) = 0 $$

Therefore, the difference in oxidation state of chromium in chromate and dichromate salts is 0.