Copper(II) oxide

Copper(II) oxide or cupric oxide is the inorganic compound with the formula CuO. A black solid, it is one of the two stable oxides of copper, the other being Cu2O or cuprous oxide. As a mineral, it is known as tenorite. It is a product of copper mining and the precursor to many other copper-containing products and chemical compounds.[3]

Copper(II) oxide
IUPAC name
Copper(II) oxide
Other names
Cupric oxide
3D model (JSmol)
ECHA InfoCard 100.013.882
RTECS number
  • GL7900000
Molar mass 79.545 g/mol
Appearance black to brown powder
Density 6.315 g/cm3
Melting point 1,326 °C (2,419 °F; 1,599 K)
Boiling point 2,000 °C (3,630 °F; 2,270 K)
Solubility soluble in ammonium chloride, potassium cyanide
insoluble in alcohol, ammonium hydroxide, ammonium carbonate
Band gap 1.2 eV
+238.9·10−6 cm3/mol
monoclinic, mS8[1]
C2/c, #15
a = 4.6837, b = 3.4226, c = 5.1288
α = 90°, β = 99.54°, γ = 90°
43 J·mol−1·K−1
−156 kJ·mol−1
Safety data sheet Fisher Scientific
Harmful (Xn)
Dangerous for the environment (N)
NFPA 704 (fire diamond)
Flash point Non-flammable
NIOSH (US health exposure limits):
PEL (Permissible)
TWA 1 mg/m3 (as Cu)[2]
REL (Recommended)
TWA 1 mg/m3 (as Cu)[2]
IDLH (Immediate danger)
TWA 100 mg/m3 (as Cu)[2]
Related compounds
Other anions
Copper(II) sulfide
Other cations
Nickel(II) oxide
Zinc oxide
Related compounds
Copper(I) oxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YN ?)
Infobox references


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 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, or basic copper(II) carbonate:[4]

2 Cu(NO3)2 → 2 CuO + 4 NO2 + O2 (180°C)


Copper(II) oxide dissolves in mineral acids such as hydrochloric acid, sulfuric acid or nitric acid to give the corresponding copper(II) salts:[4]

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[Cu(OH)4]

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

Structure and physical properties

Copper(II) oxide belongs to the monoclinic crystal system. The copper atom is coordinated by 4 oxygen atoms in an approximately square planar configuration.[1]

The work function of bulk CuO is 5.3 eV[5]


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.[3]

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 incorrectly used as a dietary supplement in animal feed.[6] Due to low bioactivity, negligible copper is absorbed.[7]

It is also used when welding with copper alloys.[8]

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").

See also


  1. The effect of hydrostatic pressure on the ambient temperature structure of CuO, Forsyth J.B., Hull S., J. Phys.: Condens. Matter 3 (1991) 5257-5261 , doi:10.1088/0953-8984/3/28/001. Crystallographic point group: 2/m or C2h. Space group: C2/c. Lattice parameters: a = 4.6837(5), b = 3.4226(5), c = 5.1288(6), α = 90°, β = 99.54(1)°, γ = 90°.
  2. NIOSH Pocket Guide to Chemical Hazards. "#0150". National Institute for Occupational Safety and Health (NIOSH).
  3. Richardson, H. Wayne (2002). "Copper Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a07_567.
  4. O. Glemser and H. Sauer (1963). "Copper, Silver, Gold". In G. Brauer (ed.). Handbook of Preparative Inorganic Chemistry, 2nd Ed. 1. NY,NY: Academic Press.
  5. F. P. Koffyberg and F. A. Benko (1982). "A photoelectrochemical determination of the position of the conduction and valence band edges of p-type CuO". J. Appl. Phys. 53 (2): 1173. doi:10.1063/1.330567.
  6. "Uses of Copper Compounds: Other Copper Compounds". Copper Development Association. 2007. Retrieved 2007-01-27.
  7. 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
  8. "Cupric Oxide Data Sheet". Hummel Croton Inc. 2006-04-21. Retrieved 2007-02-01.
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