Copper(II) Oxide
Occurrence, Production and Properties
This compound — also known as cupric oxide (CuO) — occurs naturally as the black or grey mineral tenorite. Like Cu2O, it can be made by heating copper, but at a lower temperature. This method gives an impure form, however, and it is best prepared by heating some oxygen-containing copper compounds, such as the carbonate, hydroxide, or nitrate. It is a black solid that melts above 2192°F (1200°C). At this temperature, it loses some oxygen, leaving small amounts of copper(I) oxide. Like the other form, copper(II) oxide is insoluble in most solvents, but reacts with acids, forming salts.