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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 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+
It is also attacked by concentrated alkali to yield salts of [Cr(OH) 6] 3−. When heated with finely divided carbon or aluminium, it is reduced to chromium metal: Cr 2 O 3 + 2 Al → 2 Cr + Al 2 O 3. Unlike the classic thermite reaction involving iron oxides, the chromium oxide thermite creates few or no sparks, smoke or sound, but glows brightly.
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
Its ideal shape anisotropy, which imparts high coercivity and remnant magnetization, made it a compound superior to γ-Fe 2 O 3. Chromium(IV) oxide is used to manufacture magnetic tape used in high-performance audio tape and standard audio cassettes. [93] Chromium(III) oxide (Cr 2 O 3) is a metal polish known as green rouge. [94] [95]
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]Cl(H 2 O) 6. The cation in basic iron acetate is isostructural with the cation in basic chromium acetate. Both feature octahedral metal centers conjoined by oxo and ...
Hydrated chromium(III) sulfate, Cr 2 (SO 4) 3 ·18H 2 O, (CAS #13520-66-6) is a violet solid that readily dissolves in water to give the metal aquo complex, [Cr(H 2 O) 6] 3+. 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 ...
Iron(III) chloride – FeCl 3; Iron(III) fluoride – FeF 3; Iron(III) oxalate – C 6 Fe 2 O 12; Iron(III) oxide – Fe 2 O 3; Iron(III) nitrate – Fe(NO 3) 3 (H 2 O) 9; Iron(III) sulfate – Fe 2 (SO 4) 3; Iron(III) thiocyanate – Fe(SCN) 3; Iron(II,III) oxide – Fe 3 O 4; Iron ferrocyanide – Fe 7 (CN) 18; Prussian blue (Iron(III ...