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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.
Chromium(III) hydroxide (Cr(OH) 3) is amphoteric, dissolving in acidic solutions to form [Cr(H 2 O) 6] 3+, and in basic solutions to form [Cr(OH) 6] 3−. It is dehydrated by heating to form the green chromium(III) oxide (Cr 2 O 3), a stable oxide with a crystal structure identical to that of corundum. [21]
In acid solution the aquated Cr 3+ ion is produced. Cr 2 O 2− 7 + 14 H + + 6 e − → 2 Cr 3+ + 7 H 2 O ε 0 = 1.33 V. In alkaline solution chromium(III) hydroxide is produced. The redox potential shows that chromates are weaker oxidizing agent in alkaline solution than in acid solution. [6] CrO 2− 4 + 4 H 2 O + 3 e − → Cr(OH) 3 + 5 OH −
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+
The Cr 2 (OAc) 4 (H 2 O) 2 molecule contains two atoms of chromium, two ligated molecules of water, and four acetate bridging ligands.The coordination environment around each chromium atom consists of four oxygen atoms (one from each acetate ligand) in a square, one water molecule (in an axial position), and the other chromium atom (opposite the water molecule), giving each chromium centre an ...
The formula of this compound can be written more descriptively as [Cr(H 2 O) 6] 2 (SO 4) 3 ·6H 2 O. Six of the eighteen water molecules in this formula unit are water of crystallization. Hydrated chromium(III) sulfate, Cr 2 (SO 4 ) 3 ·15(H 2 O), (CAS #10031-37-5) is a green solid that also readily dissolves in water.
The structure of the pyridine complex has been determined crystallographically. [2] Adducts with other N-heterocycles have also been characterized similarly. [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
Chromium(III) acetate, commonly known as basic chromium acetate, [2] describes a family of salts where the cation has the formula [Cr 3 O(O 2 CCH 3) 6 (OH 2) 3] +. The trichromium cation is encountered with a variety of anions, such as chloride and nitrate. Data in the table above are for the chloride hexahydrate, [Cr 3 O(O 2 CCH 3) 6 (OH 2) 3 ...