Chromium oxide

Chromium oxide
Chromium oxide
General
Systematic ; name	Chromium oxide
Traditional names	chromium oxide
Chem. formula	CrO
Physical properties
condition	black or red solid
Molar mass	68 g / mol
Thermal properties
T. melt.	1550 ° C
Classification
Reg. CAS number	12018-00-7
PubChem
Smiles
Inchi
ChemSpider
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Toxicity	Nontoxic

Chromium (II) oxide (chromium oxide) is a black or red crystals. Basic chromium oxide . Inorganic compound.

Content

1 Receiving
2 Chemical properties
3 Physical properties
4 Toxicity
5 Literature
6 Sources
7 notes

Getting

Obtained by oxidation of chromium amalgam CrHg ₃ or CrHg with nitric acid or oxygen .

{\mathsf {2CrHg_{3}+O_{2}\rightarrow 2CrO+6Hg}}

{\ displaystyle {\ mathsf {2CrHg_ {3} + O_ {2} \ rightarrow 2CrO + 6Hg}}}

Or reduction of chromium oxide (III) :

{\mathsf {H_{3}PO_{2}+2Cr_{2}O_{3}\rightarrow 4CrO+H_{3}PO_{4}}}

{\ displaystyle {\ mathsf {H_ {3} PO_ {2} + 2Cr_ {2} O_ {3} \ rightarrow 4CrO + H_ {3} PO_ {4}}}}

It is also possible to obtain by thermal decomposition of carbonyl Cr (CO) ₆

Chemical Properties

At 697 ° C it decomposes into Cr and Cr ₂ O ₃ :

{\mathsf {3CrO\rightarrow Cr_{2}O_{3}+Cr}}

{\ displaystyle {\ mathsf {3CrO \ rightarrow Cr_ {2} O_ {3} + Cr}}}

It is restored by hydrogen to metallic chromium at 1000 ° С:

{\mathsf {CrO+H_{2}\rightarrow Cr+H_{2}O}}

{\ displaystyle {\ mathsf {CrO + H_ {2} \ rightarrow Cr + H_ {2} O}}}

You can also restore coke:

{\mathsf {CrO+C\rightarrow Cr+CO}}

{\ displaystyle {\ mathsf {CrO + C \ rightarrow Cr + CO}}}

It is soluble in hydrochloric acid with the release of hydrogen and chromium (III) chloride . Insoluble in dilute sulfuric and nitric acids.

When heated in air, it quickly oxidizes to chromium (III) oxide.

Physical Properties

Exists in two polymorphic forms. It can be red (not pyrophoric) and black pyrophoric powder (self-igniting in air), so the black modification is stored under a layer of water (does not interact with water). Forms hexagonal plate crystals. Like all chromium oxides, a refractory melting point is 1550 ° C.

Toxicity

Chromium compounds with a valency of less than 6 are low toxic. The most dangerous poisons and carcinogens are chromium compounds with a valency of 6+, such as chromium oxide (VI) .

Literature

Nekrasov B.V. Fundamentals of General Chemistry. - T.1. - M .: Chemistry, 1973. - S. 380
Inorganic Compounds of Chromium: A Handbook. - L .: Chemistry, 1981. - S. 9