copper(II) oxide

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 {{chem2|[Cu(NH3)4]CO3}}. After extraction from the residues and after separation from iron, lead, etc. impurities, the carbonate salt is decomposed with steam to give CuO.

It can be formed by heating copper in air at around 300–800 °C:

: {{chem2|2 Cu + O2 → 2 CuO}}

For laboratory uses, copper(II) oxide is conveniently prepared by pyrolysis of copper(II) nitrate or basic copper(II) carbonate:{{cite book|author=O. Glemser and H. Sauer |chapter=Copper, Silver, Gold|title=Handbook of Preparative Inorganic Chemistry, 2nd Ed. |editor=G. Brauer|publisher=Academic Press|year=1963|place=NY, NY|volume=1}}

: {{chem2|2 Cu(NO3)2 → 2 CuO + 4 NO2 + O2}} (180°C)

: {{chem2|Cu2(OH)2CO3 → 2 CuO + CO2 + H2O}}

Dehydration of cupric hydroxide has also been demonstrated:

:{{chem2|Cu(OH)2 → CuO + H2O}}

Copper(II) oxide reacts with mineral acids such as hydrochloric acid, sulfuric acid, and nitric acid to give the corresponding hydrated copper(II) salts:

: 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.

Copper(II) oxide belongs to the monoclinic crystal system. The copper atom is coordinated by 4 oxygen atoms in an approximately square planar configuration.

The work function of bulk CuO is 5.3 eV.{{cite journal|journal=J. Appl. Phys.|volume=53|page=1173|year=1982|doi=10.1063/1.330567|author=F. P. Koffyberg and F. A. Benko|title=A photoelectrochemical determination of the position of the conduction and valence band edges of p-type CuO|issue=2|bibcode=1982JAP....53.1173K}}

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.

Cupric oxide is used as a pigment in ceramics to produce blue, red, and green, and sometimes gray, pink, or black glazes.

It is incorrectly used as a dietary supplement in animal feed.{{cite web|title = Uses of Copper Compounds: Other Copper Compounds|publisher = Copper Development Association|year = 2007|url = http://www.copper.org/applications/compounds/other_compounds.html|access-date = 2007-01-27|archive-date = 2013-08-15|archive-url = https://web.archive.org/web/20130815084358/http://www.copper.org/applications/compounds/other_compounds.html|url-status = dead}} Due to low bioactivity, negligible copper is absorbed.{{cite journal|doi=10.1093/jn/129.12.2278 |title=Cupric Oxide Should Not be Used as a Copper Supplement for Either Animals or Humans |date=1999 |last1=Baker |first1=David H. |journal=The Journal of Nutrition |volume=129 |issue=12 |pages=2278–2279 |pmid=10573563 |doi-access=free }}

It is used when welding with copper alloys.{{cite web|title = Cupric Oxide Data Sheet|publisher = Hummel Croton Inc.|date = 2006-04-21|url = http://www.axxousa.com/data/cuox_d.html|access-date = 2007-02-01|archive-date = 2011-07-07|archive-url = https://web.archive.org/web/20110707202129/http://www.axxousa.com/data/cuox_d.html|url-status = dead}}

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").

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.

An example of natural copper(I,II) oxide is the mineral paramelaconite, Cu⁺₂Cu²⁺₂O₃.{{Cite web|url=https://www.mindat.org/min-3098.html|title=Paramelaconite}}{{Cite web|url=https://www.ima-mineralogy.org/Minlist.htm|title=List of Minerals|date=21 March 2011}}

• Patina
• Tenorite

{{reflist|30em}}

{{Commons category|Copper(II) oxide}}

• [https://web.archive.org/web/20080302034606/http://www.npi.gov.au/database/substance-info/profiles/27.html National Pollutant Inventory - Copper and compounds fact sheet]
• [http://copperoxides.altervista.org/ Copper oxides project page] {{Webarchive|url=https://web.archive.org/web/20110725001301/http://copperoxides.altervista.org/ |date=2011-07-25 }}
• [https://www.cdc.gov/niosh/npg/npgd0151.html CDC - NIOSH Pocket Guide to Chemical Hazards]

{{Copper compounds}}

{{Oxides}}

{{Oxygen compounds}}

Category:Copper(II) compounds

Category:Semiconductor materials

Category:Pyrotechnic colorants

Category:Transition metal oxides

Category:Glass dyes