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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+
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+
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 ...
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.
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 ...
Chromium(II) Cr 2+ bright blue Chromium(III) Cr 3+ blue-green-grey Chromium(III) hydroxide: Cr(OH) 6 3− yellowish Monochromate: CrO 2− 4 yellow Dichromate: Cr 2 O 2− 7 orange Manganese(II) Mn 2+ pale pink Manganese(III) Mn 3+ crimson Manganate(V) MnO 3− 4 deep blue Manganate(VI) MnO 2− 4 dark green Manganate(VII) (permanganate) MnO ...