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 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 pinkis ...

, the other being Cu₂O or

copper(I) oxide Copper(I) oxide or cuprous oxide is the inorganic compound with the formula Cu2O. It is one of the principal oxides of copper, the other being or copper(II) oxide or cupric oxide (CuO). This red-coloured solid is a component of some antifoulin ...

(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. (2 ...

, it is known as

tenorite Tenorite is a copper oxide mineral with the chemical formula CuO. Occurrence Tenorite occurs in the weathered or oxidized zone associated with deeper primary copper sulfide orebodies. Tenorite commonly occurs with chrysocolla and the copper c ...

. 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 Pyrometallurgy is a branch of extractive metallurgy. It consists of the thermal treatment of minerals and metallurgical ores and concentrates to bring about physical and chemical transformations in the materials to enable recovery of valuable ...

, as one stage in extracting copper from its ores. The ores are treated with an aqueous mixture of

ammonium carbonate Ammonium carbonate is a salt with the chemical formula (NH4)2CO3. Since it readily degrades to gaseous ammonia and carbon dioxide upon heating, it is used as a leavening agent and also as smelling salt. It is also known as baker's ammonia and is ...

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 nitrogenous wa ...

, 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 ...

to give copper(I) and copper(II)

ammine complex In coordination chemistry, metal ammine complexes are metal complexes containing at least one ammonia () ligand. "Ammine" is spelled this way due to historical reasons; in contrast, alkyl or aryl bearing ligands are spelt with a single "m". Almost ...

es, 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) nitrate describes any member of the family of inorganic compounds with the formula Cu( NO3)2(H2O)x. The hydrates are blue solids. Anhydrous copper nitrate forms blue-green crystals and sublimes in a vacuum at 150-200 °C. Common hy ...

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 Basic copper carbonate is a chemical compound, more properly called copper(II) carbonate hydroxide. It is an ionic compound (a salt) consisting of the ions copper(II) , carbonate , and hydroxide . The name most commonly refers to the compound w ...

: : 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 acid A mineral acid (or inorganic acid) is an acid derived from one or more inorganic compounds, as opposed to organic acids which are acidic, organic compounds. All mineral acids form hydrogen ions and the conjugate base when dissolved in water. Cha ...

s 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 Acid strength is the tendency of an acid, symbol ...

, 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 nitri ...

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 simple ...

, 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 mak ...

: : 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 brie ...

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 ...

. 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 compou ...

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. 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 Copper alloys are metal alloys that have copper as their principal component. They have high resistance against corrosion. The best known traditional types are bronze, where tin is a significant addition, and brass, using zinc instead. Both of ...

. A copper oxide electrode formed part of the early battery type known as the

Edison–Lalande cell The Edison–Lalande cell was a type of alkaline primary battery developed by Thomas Edison from an earlier design by Felix Lalande and Georges Chaperon. It consisted of plates of copper oxide and zinc in a solution of potassium hydroxide. The ...

. Copper oxide was also used in a lithium battery 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-specifi ...

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, 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