Copper(II) oxide or cupric oxide is an

inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemi ...

with the formula CuO. A black solid, it is one of the two stable oxides of

copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish ...

, the other being Cu₂O or copper(I) oxide (cuprous oxide). As a

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. ...

, it is known as tenorite. It is a product of

copper mining Copper extraction refers to the methods used to obtain copper from its ores. The conversion of copper consists of a series of physical and electrochemical processes. Methods have evolved and vary with country depending on the ore source, loca ...

and the precursor to many other copper-containing products and chemical compounds.

Production

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 Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogeno ...

, and

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as we ...

to give copper(I) and copper(II) ammine complexes, which are extracted from the solids. These complexes are decomposed with steam to give CuO. It can be formed by heating copper in air at around 300–800°C: : 2 Cu + O₂ → 2 CuO For laboratory uses, pure copper(II) oxide is better prepared by heating copper(II) nitrate,

copper(II) hydroxide Copper(II) hydroxide is the hydroxide of copper with the chemical formula of Cu(OH)2. It is a pale greenish blue or bluish green solid. Some forms of copper(II) hydroxide are sold as "stabilized" copper(II) hydroxide, although they likely consist ...

, or basic copper(II) carbonate: : 2 Cu(NO₃)_2(s) → 2 CuO_(s) + 4 NO_2(g) + O_2(g) (180°C) : Cu₂(OH)₂CO_3(s) → 2 CuO_(s) + CO_2(g) + H₂O_(g) : Cu(OH)_2(s) → CuO_(s) + H₂O_(g)

Reactions

Copper(II) oxide dissolves in mineral acids such as

hydrochloric acid Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid. It is a component of the gastric acid in the dig ...

, sulfuric acid or

nitric acid Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available ni ...

to give the corresponding copper(II) salts: : CuO + 2 HNO₃ → Cu(NO₃)₂ + H₂O : CuO + 2 HCl → CuCl₂ + H₂O : CuO + H₂SO₄ → CuSO₄ + H₂O It reacts with concentrated alkali to form the corresponding cuprate salts: : 2 MOH + CuO + H₂O → M₂ u(OH)₄ It can also be reduced to

metal using

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...

carbon monoxide Carbon monoxide ( chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the si ...

, or

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon makes ...

: : CuO + H₂ → Cu + H₂O : CuO + CO → Cu + CO₂ : 2 CuO + C → 2Cu + CO₂ When cupric oxide is substituted for iron oxide in

thermite Thermite () is a pyrotechnic composition of metal powder and metal oxide. When ignited by heat or chemical reaction, thermite undergoes an exothermic reduction-oxidation (redox) reaction. Most varieties are not explosive, but can create br ...

the resulting mixture is a low explosive, not an incendiary.

Structure and physical properties

Copper(II) oxide belongs to the

monoclinic crystal system In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in the orthorhombic sys ...

. The copper atom is coordinated by 4 oxygen atoms in an approximately square planar configuration. The

work function In solid-state physics, the work function (sometimes spelt workfunction) is the minimum thermodynamic work (i.e., energy) needed to remove an electron from a solid to a point in the vacuum immediately outside the solid surface. Here "immediately" ...

of bulk CuO is 5.3 eV

Uses

As a significant product of copper mining, copper(II) oxide is the starting point for the production of other copper salts. For example, many wood preservatives are produced from copper oxide. Cupric oxide is used as a

pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic comp ...

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 Animal feed is food given to domestic animals, especially livestock, in the course of animal husbandry. There are two basic types: fodder and forage. Used alone, the word ''feed'' more often refers to fodder. Animal feed is an important input to ...

. Due to low bioactivity, negligible copper is absorbed. Cupric Oxide Should Not Be Used As a Copper Supplement for Either Animals or Humans, Baker, D. H., J. Nutr. 129, 12 (1999) 2278-2279 It is used when welding with copper alloys. 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 Lithium battery may refer to: * Lithium metal battery, a non-rechargeable battery with lithium as an anode ** Rechargeable lithium metal battery, a rechargeable counterpart to the lithium metal battery * Lithium-ion battery, a rechargeable bat ...

type (

IEC 60086 Standard battery nomenclature describes portable dry cell batteries that have physical dimensions and electrical characteristics interchangeable between manufacturers. The long history of disposable dry cells means that many manufacturer-specif ...

code "G").

Pyrotechnics and fireworks

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 compounds

An example of natural copper(I,II) oxide is the mineral

paramelaconite Paramelaconite is a rare, black-colored copper(I,II) oxide mineral with formula CuCuO3 (or Cu4O3). It was discovered in the Copper Queen Mine in Bisbee, Arizona, about 1890. It was described in 1892 and more fully in 1941. Its name is derived fro ...

, Cu⁺₂Cu²⁺₂O₃.

References

External links

National Pollutant Inventory - Copper and compounds fact sheet

Copper oxides project page
{{Oxygen compounds Copper(II) compounds Semiconductor materials Pyrotechnic colorants Transition metal oxides Glass dyes