Copper(II)_oxide

Copper(II) oxide

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

Chemistry

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, but in this case it is formed along with copper(I) oxide; thus, it is better prepared by heating copper(II) nitrate, copper(II) hydroxide or copper(II) carbonate:

2Cu(NO₃)₂ → 2CuO + 4NO₂ + O₂

Cu(OH)₂(s) → CuO(s) + H₂O(l)

CuCO₃ → CuO + CO₂

Copper(II) oxide is a basic oxide, so it dissolves in mineral acids such as hydrochloric acid, sulfuric acid or nitric acid to give the corresponding copper(II) salts:

CuO + 2HNO₃ → Cu(NO₃)₂ + H₂O

CuO + 2HCl → CuCl₂ + H₂O

CuO + H₂SO₄ → CuSO₄ + H₂O

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

CuO + H₂ → Cu + H₂O

CuO + CO → Cu + CO₂

It is also made by reacting solid copper with oxygen gas.

2Cu + O₂ → 2CuO

Crystal structure

Copper(II) oxide belongs to the monoclinic crystal system, with a crystallographic point group of 2/m or C_2h. 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°. The copper atom is coordinated by 4 oxygen atoms in an approximately square planar configuration.


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 can cause irritation and damage to the corneas, and potentially can cause conjunctivitis. Contact to the skin can cause irritation and discoloration. Ingesting cupric oxide can lead to central nervous system depression, liver and kidney damage, gastro-intestinal damage, circulatory system failure or damage to the vascular system. Inhalation can lead to damage to the lungs and septum. Inhalation of fumes of cupric oxide can lead to a disease called Metal fume fever, which has symptoms similar to influenza. Prolonged exposure to cupric oxide can lead to dermatitis, and can cause a toxic build-up of copper in people with Wilson's disease. Handling copper(II) oxide should be done in well ventilated area, and care should be taken to avoid contact with the skin or eyes. After handling, one should wash thoroughly.

Uses

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. 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 oxide can be used to produce other copper salts. It is also used when welding with copper alloys.

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.