Knowra Chromate and dichromate Chromate and dichromate Chromate (CrO₄²⁻) and dichromate (Cr₂O₇²⁻) are chromium(VI) oxyanions linked by pH-dependent equilibria; chromate solutions are yellow and dichromate solutions orange.
Chromium(VI) : Chromium in the +6 oxidation state, commonly found in oxygen-containing compounds. Both ions contain chromium in this oxidation state.
Oxyanion : A negatively charged polyatomic ion containing oxygen bonded to another element. Chromate and dichromate are oxygen-rich anions centered on chromium.
Potassium dichromate : An orange crystalline salt, K₂Cr₂O₇, containing dichromate ions and chromium(VI). It is a common laboratory source of dichromate for analytical and chemical reactions.
Chromium(III) : Chromium in the +3 oxidation state, common in stable salts and coordination complexes. It contrasts with the strongly oxidizing chromium(VI) present in chromate and dichromate.
Chromium contamination : Environmental pollution by chromium compounds in soil, water, or air. Soluble chromate and dichromate can contribute to chromium(VI) contamination.
Acid–base equilibrium : A reversible proton-transfer process whose position depends on acidity and the substances present. Adding acid shifts chromate toward protonated and condensed forms, including dichromate.
Oxidation state : A formal number assigned to an atom to track electron accounting in compounds and ions. It identifies chromium as +6 in both oxyanions.
Chromate coating : A corrosion-protective surface treatment that uses chromium-containing conversion layers, often involving chromium(VI). Chromate chemistry has been used to protect metal surfaces from corrosion.
Chromite : The mineral FeCr₂O₄, the principal ore of chromium. Despite the similar name, chromite is a mineral, not the chromate oxyanion.
Groundwater remediation : Methods for removing or immobilizing contaminants in underground water supplies. Treatment often converts soluble chromium(VI) into less mobile chromium(III).
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