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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+
Another possibility is the molecular autoionization reaction between two water molecules, in which one water molecule acts as an acid and another as a base. H 2 O + H 2 O ⇌ H 3 O + + HO −. The bicarbonate ion, HCO − 3, is amphoteric as it can act as either an acid or a base: As an acid, losing a proton: HCO − 3 + OH − ⇌ CO 2− 3 ...
This kind of reaction is also observed with solutions of chrome alum and other water-soluble chromium(III) salts. A tetrahedral coordination of chromium(III) has been reported for the Cr-centered Keggin anion [α-CrW 12 O 40] 5–. [11] Chromium(III) hydroxide (Cr(OH) 3) is amphoteric, dissolving in acidic solutions to form [Cr(H 2 O) 6] 3 ...
A large number of chromium(III) compounds are known, such as chromium(III) nitrate, chromium(III) acetate, and chromium(III) oxide. [33] Chromium(III) can be obtained by dissolving elemental chromium in acids like hydrochloric acid or sulfuric acid, but it can also be formed through the reduction of chromium(VI) by cytochrome c7. [34] The Cr 3+
Further condensation reactions can occur in strongly acidic solution with the formation of trichromates, Cr 3 O 2− 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−
The following chart shows the solubility of various ionic compounds in water at 1 atm pressure and room temperature (approx. 25 °C, 298.15 K). "Soluble" means the ionic compound doesn't precipitate, while "slightly soluble" and "insoluble" mean that a solid will precipitate; "slightly soluble" compounds like calcium sulfate may require heat to precipitate.
A variety of other chromium(III) sulfates are known, but also contain hydroxide or oxide ligands. Most important commercially is basic chromium sulfate, which is thought to be [Cr 2 (H 2 O) 6 (OH) 4]SO 4 (CAS#39380-78-4). [2] It results from the partial neutralization of the hexahydrates. Other chromium(III) hydroxides have been reported. [3]
Solutions of metal aquo complexes are acidic owing to the ionization of protons from the water ligands. In dilute solution chromium(III) aquo complex has a pK a of about 4.3, affording a metal hydroxo complex: [Cr(H 2 O) 6] 3+ ⇌ [Cr(H 2 O) 5 (OH)] 2+ + H + Thus, the aquo ion is a weak acid, of comparable strength to acetic acid (pK a of about ...