Chromate

Chromates and Dichromates are salts of chromic acid and dichromic acid, respectively.

The chromium atoms are in oxidation state VI in both, and the chromate and dichromate ions are fairly strong oxidizing agents.

In an aqueous solution, yellow chromate (CrO₄^2-) and orange dichromate (Cr₂O₇^2-) ions are in a chemical equilibrium. This equilibrium is pushed towards dichromate by lowering the pH (making the solution more acidic) - a classic demonstration of Le Chatelier's principle.

2 CrO₄^2- + 2 H₃O⁺ → Cr₂O₇^2- + 3 H₂O

They are used in environmental analysis to measure chemical oxygen demand (COD).

They are carcinogenic.