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Copper(II) oxide or cupric oxide is an inorganic compound with the formula CuO. A black solid, it is one of the two stable oxides of copper, the other being Cu2O or copper(I) oxide (cuprous oxide). As a mineral, it is known as tenorite, or sometimes black copper. It is a product of copper mining and the precursor to many other copper-containing products and chemical compounds.<ref name=Ullmann>Template:Ullmann</ref>
ProductionEdit
It is produced on a large scale by pyrometallurgy, as one stage in extracting copper from its ores. The ores are treated with an aqueous mixture of ammonium carbonate, ammonia, and oxygen to ultimately give copper(II) ammine complex carbonates, such as Template:Chem2. After extraction from the residues and after separation from iron, lead, etc. impurities, the carbonate salt is decomposed with steam to give CuO.<ref name=Ullmann/>
It can be formed by heating copper in air at around 300–800 °C:
For laboratory uses, copper(II) oxide is conveniently prepared by pyrolysis of copper(II) nitrate or basic copper(II) carbonate:<ref name=Brauer>Template:Cite book</ref>
- Template:Chem2 (180°C)
- Template:Chem2
Dehydration of cupric hydroxide has also been demonstrated:
ReactionsEdit
Copper(II) oxide reacts with mineral acids such as hydrochloric acid, sulfuric acid, and nitric acid to give the corresponding hydrated copper(II) salts:<ref name=Brauer/>
- CuO + 2 HNO3 → Cu(NO3)2 + H2O
- CuO + 2 HCl → CuCl2 + H2O
- CuO + H2SO4 → CuSO4 + H2O
In presence of water it reacts with concentrated alkali to form the corresponding cuprate salts:
- 2 NaOH + CuO + H2O → Na2[Cu(OH)4]
It can also be reduced to copper metal using hydrogen, carbon monoxide, and carbon:
- CuO + H2 → Cu + H2O
- CuO + CO → Cu + CO2
- 2 CuO + C → 2Cu + CO2
When cupric oxide is substituted for iron oxide in thermite the resulting mixture is a low explosive, not an incendiary.
Structure and physical propertiesEdit
Copper(II) oxide belongs to the monoclinic crystal system. The copper atom is coordinated by 4 oxygen atoms in an approximately square planar configuration.<ref name= "Hull"/>
The work function of bulk CuO is 5.3 eV.<ref>Template:Cite journal</ref>
UsesEdit
As a significant product of copper mining, copper(II) oxide is the starting point for the production of many other copper salts. For example, many wood preservatives are produced from copper oxide.<ref name=Ullmann/>
Cupric oxide is used as a pigment in ceramics to produce blue, red, and green, and sometimes gray, pink, or black glazes.<ref name=Ullmann/>
It is incorrectly used as a dietary supplement in animal feed.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Due to low bioactivity, negligible copper is absorbed.<ref name= "Baker">Template:Cite journal</ref>
It is used when welding with copper alloys.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
A copper oxide electrode formed part of the early battery type known as the Edison–Lalande cell. Copper oxide was also used in a lithium battery type (IEC 60086 code "G").
Pyrotechnics and fireworksEdit
Used as moderate blue coloring agent in blue flame compositions with additional chlorine donors and oxidizers such as chlorates and perchlorates. Providing oxygen it can be used as flash powder oxidizer with metal fuels such as magnesium, aluminium, or magnalium powder. Sometimes it is used in strobe effects and thermite compositions as crackling stars effect.
Similar compoundsEdit
An example of natural copper(I,II) oxide is the mineral paramelaconite, Cu+2Cu2+2O3.<ref name=Mindat>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name=IMA>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
See alsoEdit
ReferencesEdit
External linksEdit
- National Pollutant Inventory - Copper and compounds fact sheet
- Copper oxides project page Template:Webarchive
- CDC - NIOSH Pocket Guide to Chemical Hazards
Template:Copper compounds Template:Oxides Template:Oxygen compounds