Copper(II) oxide or cupric oxide is an

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

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

oxide An oxide () is a chemical compound containing at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion (anion bearing a net charge of −2) of oxygen, an O2− ion with oxygen in the oxidation st ...

s of

copper Copper is a chemical element; it has symbol Cu (from Latin ) 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-orang ...

, 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 substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...

, it is known as tenorite, or sometimes black copper. It is a product of

copper mining Copper extraction is the multi-stage process of obtaining copper from list of copper ores, its ores. The conversion of copper ores consists of a series of physical, chemical, and electrochemical processes. Methods have evolved and vary with coun ...

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 chemical compound of nitrogen and hydrogen with the chemical formula, formula . A Binary compounds of hydrogen, stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pu ...

, and

oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...

to ultimately give copper(II) ammine complex carbonates, such as . 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: : For laboratory uses, copper(II) oxide is conveniently prepared by pyrolysis of

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 hygroscopic blue solids. Anhydrous copper nitrate forms blue-green crystals and sublimes in a vacuum at 150-200 ° ...

or basic copper(II) carbonate: : (180°C) : Dehydration of cupric hydroxide has also been demonstrated: :

Reactions

Copper(II) oxide reacts with

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. Ch ...

s such as

hydrochloric acid Hydrochloric acid, also known as muriatic acid or spirits of salt, is an aqueous solution of hydrogen chloride (HCl). It is a colorless solution with a distinctive pungency, pungent smell. It is classified as a acid strength, strong acid. It is ...

sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, ...

, and

nitric acid Nitric acid is an inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but samples tend to acquire a yellow cast over time due to decomposition into nitrogen oxide, oxides of nitrogen. Most com ...

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 In chemistry, an alkali (; from the Arabic word , ) is a basic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of a soluble base has a pH greater than 7.0. The a ...

to form the corresponding cuprate salts: : 2 NaOH + CuO + H₂O → Na₂ u(OH)₄ It can also be reduced to

metal using

hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

carbon monoxide Carbon monoxide (chemical formula CO) is a poisonous, flammable gas that is colorless, odorless, tasteless, and 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 ...

, and

carbon Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...

: : 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 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 sy ...

. 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 spelled 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 many other copper salts. For example, many

wood preservative Wood preservation refers to any method or process, or even technique, used to protect the wood and extend its service life. Most wood species are susceptible to both biological (''biotic'') and non-biological (''abiotic'') factors that cause d ...

s are produced from copper oxide. Cupric oxide is used as a

pigment A pigment is a powder used to add or alter color or change visual appearance. Pigments are completely or nearly solubility, insoluble and reactivity (chemistry), chemically unreactive in water or another medium; in contrast, dyes are colored sub ...

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 ...

. Due to low bioactivity, negligible copper is absorbed. It is used when welding with

copper alloys Copper alloys are metal Alloy, alloys that have copper as their principal component. They have high resistance against corrosion. Of the large number of different types, the best known traditional types are bronze, where tin is a significant addi ...

. 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 ** Lithium–air battery ** Lithium–iron disulfide battery ** Lithium–sulfur battery ** Nickel–lithium battery ** Rechargeable li ...

type ( IEC 60086 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

Production

Reactions

Structure and physical properties

Uses

Pyrotechnics and fireworks

Similar compounds

See also

References

External links