Cupric oxide

Copper(II) oxide
CAS number 1317-38-0 YesY
PubChem 14829
ChemSpider 144499 YesY
RTECS number GL7900000
Jmol-3D images Image 2
Molecular formula CuO
Molar mass 79.545 g/mol
Appearance black to brown powder
Density 6.315 g/cm3
Melting point

1326 °C, 1599 K, 2419 °F

Boiling point

2000 °C, 2273 K, 3632 °F

Solubility in water insoluble
Solubility soluble in ammonium chloride, potassium cyanide
insoluble in alcohol, ammonium hydroxide, ammonium carbonate
Band gap 1.2 eV
Refractive index (nD) 2.63
Crystal structure monoclinic, mS8[1]
Space group C2/c, #15
Lattice constant a = 4.6837, b = 3.4226, c = 5.1288
Lattice constant α = 90°, β = 99.54°, γ = 90°
Std enthalpy of
−156 kJ·mol−1
Standard molar
43 J·mol−1·K−1
MSDS Fischer Scientific
EU Index Not listed
EU classification Harmful (Xn)
Dangerous for the environment (N)
NFPA 704
Flash point Non-flammable
Related compounds
Other anions Copper(II) sulfide
Other cations Nickel(II) oxide
Zinc oxide
Related compounds Copper(I) oxide
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Copper(II) oxide or cupric oxide (CuO) is the higher oxide of copper. As a mineral, it is known as tenorite.


It is a black solid with an ionic structure which melts above 1200 °C with some loss of oxygen. It can be formed by heating copper in air:

2 Cu + O2 → 2 CuO

although in this case copper(I) oxide is formed as well. Pure Copper(II) oxide is better prepared by heating copper(II) nitrate, copper(II) hydroxide or copper(II) carbonate:

2 Cu(NO3)2 → 2 CuO + 4 NO2 + O2
Cu(OH)2 (s) → CuO (s) + H2O (l)
CuCO3 → CuO + CO2

Copper(II) oxide is a amphoteric oxide, so it dissolves in mineral acids such as hydrochloric acid, sulfuric acid or nitric acid 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 XOH + CuO + H2O → X2[Cu(OH)4]

It can also be reduced to copper metal using hydrogen or carbon monoxide:

CuO + H2 → Cu + H2O
CuO + CO → Cu + CO2

A laboratory method for preparing copper(II) oxide is to electrolyze water containing sodium bicarbonate at a moderate voltage with a copper anode, collect the mixture of insoluble copper hydroxide, basic copper carbonate, and copper carbonate precipitates, and heat it to release the hydrogen, carbon and excess oxygen.

Crystal structure

Copper(II) oxide belongs to the monoclinic crystal system, with a crystallographic point group of 2/m or C2h. The space group of its unit cell is C2/c, and its lattice parameters are a = 4.6837(5), b = 3.4226(5), c = 5.1288(6), α = 90°, β = 99.54(1)°, γ = 90°.[1] The copper atom is coordinated by 4 oxygen atoms in an approximately square planar configuration.[1]

the unit cell of copper(II) oxide
part of the crystal structure of CuO

Health effects

Copper(II) oxide is an irritant. It also can cause damage to the endocrine and central nervous system. Contact to the eyes or skin can cause irritation. Ingesting cupric oxide powder can result in a metallic taste, nausea, vomiting and stomach pain. In more severe cases, there may be blood in vomit or black or tarry stools, jaundice and enlarged liver. Blood cells rupture resulting in circulatory collapse and shock. Inhalation can lead to damage to the lungs and septum. Inhalation of fumes during smelting of cupric oxide powder can lead to a disease called metal fume fever, which can result in flu like symptoms. Copper (II) oxide can cause a toxic build-up of copper in a small subset of the population with Wilson's disease. Handling copper (II) oxide powder should be done in well ventilated area, and care should be taken to avoid contact with the skin or eyes.[2] However copper is an essential trace element for the normal function of many tissues, including the nervous system, immune system, heart, skin and for the formation of capillaries [3][4] as well as copper being extremely well metabolized by humans. Copper (II) oxide (Cupric oxide, not Cuprous oxide) has extremely low bioavailability (practically zero) and should not be taken in conditions of copper deficiency, especially as part of a multivitamin which also includes zinc or molybdenum.[5] Excessive zinc or molybdenum intake eliminates copper from the body. Copper oxide is used in vitamins supplements as a safe source of copper[6] and over-the-counter treatments. Copper oxide is also used in consumer products such as pillowcases and socks, due to its cosmetic and anti-microbial properties.[7][8][9][10] The risk of dermal sensitivity to copper is considered extremely minimal.[11]


Cupric oxide is used as a pigment in ceramics to produce blue, red, and green (and sometimes gray, pink, or black) glazes. It is also used to produce cuprammonium hydroxide solutions, used to make rayon. It is also occasionally used as a dietary supplement in animals, against copper deficiency.[12] Copper(II) oxide has application as a p-type semiconductor, because it has a narrow band gap of 1.2 eV. It is an abrasive used to polish optical equipment. Cupric oxide can be used to produce dry cell batteries. It has also been used in wet cell batteries as the cathode, with lithium as an anode, and dioxalane mixed with lithium perchlorate as the electrolyte. Copper(II) oxide can be used to produce other copper salts. It is also used when welding with copper alloys.[13]

Another use for cupric oxide is as a substitute for iron oxide in thermite. This can turn the thermite from an incendiary to a low explosive.

Use in disposal

Cupric oxide can be used to safely dispose of hazardous materials such as cyanide, hydrocarbons, halogenated hydrocarbons and dioxins, through oxidation.[14]

Here are equations depicting the decomposition of phenol and pentachlorophenol, respectively, with copper oxide:

C6H5OH + 14CuO → 6CO2 + 3H2O + 14Cu
C6Cl5OH + 2H2O + 9CuO → 6CO2 + 5HCl + 9Cu


See also


External links

  • National Pollutant Inventory - Copper and compounds fact sheet
  • Copper oxides project page
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