# How do we differentiate solutions of "sodium dichromate" and "chromium (III+)" ion?

Apr 23, 2017

Perhaps you should tell us this...........

#### Explanation:

Dichromate ion is $C {r}_{2} {O}_{7}^{2 -}$. An oxygen bridges 2 metal centres to give a complex ion that I could represent as:

""^(-)O(""_2O=)Cr-O-Cr(=O)_2O^(-).

The oxidation state of each chromium centre is $V I +$ (the maximum oxidation number), and this reagent is commonly used an oxidant, and we see the colour of bright orange (the dichromate ion) change to green, $C {r}^{3 +}$.

Dichromate salts are typically a beautiful orange colour: