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Predominance diagram for chromate. In aqueous solution, chromate and dichromate anions exist in a chemical equilibrium.. 2 CrO 2− 4 + 2 H + ⇌ Cr 2 O 2− 7 + H 2 O. The predominance diagram shows that the position of the equilibrium depends on both pH and the analytical concentration of chromium.
Chromate anions (CrO 2− 4) and dichromate (Cr 2 O 7 2−) anions are the principal ions at this oxidation state. They exist at an equilibrium, determined by pH: 2 [CrO 4] 2− + 2 H + ⇌ [Cr 2 O 7] 2− + H 2 O. Chromium(VI) oxyhalides are known also and include chromyl fluoride (CrO 2 F 2) and chromyl chloride (CrO
While chromium metal and Cr(III) ions are considered non-toxic, chromate and its derivatives, often called "hexavalent chromium", is toxic and carcinogenic. According to the European Chemicals Agency (ECHA), chromium trioxide that is used in industrial electroplating processes is a "substance of very high concern" (SVHC). [16]
For other compounds of chromium(III) as a means of distinguishing a chemical species such as hexacyanochromite(III). [Cr(CN) 6] 3− from an analogous compound in which chromium is a different oxidation state. The mineral chromite is an iron chromium oxide with empirical formula FeCr 2 O 4. Structurally, it belongs to the spinel group.
Potassium chromate is the inorganic compound with the formula K 2 CrO 4. This yellow solid is the potassium salt of the chromate anion. It is a common laboratory chemical, whereas sodium chromate is important industrially.
An oxyanion, or oxoanion, is an ion with the generic formula A x O z− y (where A represents a chemical element and O represents an oxygen atom). Oxyanions are formed by a large majority of the chemical elements. [1] The formulae of simple oxyanions are determined by the octet rule. The corresponding oxyacid of an oxyanion is the compound H z ...
Silver chromate is an inorganic compound with formula Ag 2 CrO 4 which appears as distinctively coloured brown-red crystals. The compound is insoluble and its precipitation is indicative of the reaction between soluble chromate and silver precursor salts (commonly potassium / sodium chromate with silver nitrate ).
Zinc chromate, Zn Cr O 4, is a chemical compound, a salt containing the chromate anion, appearing as odorless yellow powder or yellow-green crystals, but, when used for coatings, pigments are often added. [2] [3] [4] It is used industrially in chromate conversion coatings, having been developed by the Ford Motor Company in the 1920s. [5]