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Chromium compounds are compounds containing the element chromium (Cr). Chromium is a member of group 6 of the transition metals . The +3 and +6 states occur most commonly within chromium compounds, followed by +2; charges of +1, +4 and +5 for chromium are rare, but do nevertheless occasionally exist.
[3] Aqueous chromium(VI) oxide peroxide decomposes in a few seconds, turning green as chromium(III) compounds are formed. [4] 2 CrO(O 2) 2 + 7 H 2 O 2 + 6 H + → 2 Cr 3+ + 10 H 2 O + 7 O 2. Stable adducts of the type CrO(O 2) 2 L include those with L = diethyl ether, 1-butanol, ethyl acetate, or amyl acetate. They form by adding a layer of the ...
10, and tetrachromates, Cr 4 O 2− 13. [2] All polyoxyanions of chromium(VI) have structures made up of tetrahedral CrO 4 units sharing corners. [3] The hydrogen chromate ion, HCrO 4 −, is a weak acid: HCrO − 4 ⇌ CrO 2− 4 + H +; pK a ≈ 5.9. It is also in equilibrium with the dichromate ion: 2 HCrO − 4 ⇌ Cr 2 O 2− 7 + H 2 O
Potassium peroxochromate is prepared by treating potassium chromate with hydrogen peroxide at 0 °C: . 2 CrO 2− 4 + 8 H 2 O 2 → 2 [Cr(O 2) 4] 2− + 8 H 2 O. The intermediate tetraperoxochromate(VI) is reduced by hydrogen peroxide, forming tetraperoxochromate(V): [3] [4]
Potassium peroxochromate (K 3 [Cr(O 2) 4]) is made by reacting potassium chromate with hydrogen peroxide at low temperatures. This red brown compound is stable at room temperature but decomposes spontaneously at 150–170 °C. [38]
The Parisians Pannetier and Binet first prepared the transparent hydrated form of Cr 2 O 3 in 1838 via a secret process, sold as a pigment. [6] It is derived from the mineral chromite, (Fe,Mg)Cr 2 O 4. The conversion of chromite to chromia proceeds via Na 2 Cr 2 O 7, which is reduced with sulfur at high temperatures: [7] Na 2 Cr 2 O 7 + S → ...
Hydrogen peroxide is a chemical compound with the formula H 2 O 2.In its pure form, it is a very pale blue [5] liquid that is slightly more viscous than water.It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3%–6% by weight) in water for consumer use and in higher concentrations for industrial use.
Chromium(III) hydroxide is a gelatinous green inorganic compound with the chemical formula Cr(OH) 3. It is a polymer with an undefined structure and low solubility. It is amphoteric, dissolving in both strong alkalis and strong acids. [2] In alkali: Cr(OH) 3 + OH − → CrO − 2 + 2 H 2 O In acid: Cr(OH) 3 (OH 2) 3 + 3 H + → Cr(OH 2) 6 3+