Chemistry of Cupric Oxide

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

Here, it is formed along with copper(I) oxide as a side product; thus, it 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 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 + 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 copper hydroxide, basic copper carbonate, and copper carbonate produced, and heat it.

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