Copper(II) carbonate
Copper(II) carbonate is an inorganic compound with the chemical formula CuCO3. While the formula CuCO3 is often used to describe "copper carbonate," it actually refers to a basic copper carbonate, specifically either malachite (Cu2CO3(OH)2) or azurite (Cu3(CO3)2(OH)2), which are more stable forms found naturally as minerals.
True, pure copper(II) carbonate (CuCO3) is a green to bluish-green solid, but it is unstable and readily decomposes. It is practically insoluble in water and organic solvents. However, it will dissolve in acids, forming copper(II) salts and releasing carbon dioxide. It also dissolves in solutions of ammonia and alkali metal cyanides.
The instability of pure CuCO3 under normal conditions makes it difficult to isolate in pure form. It is typically prepared by reacting copper(II) salts with alkali metal carbonates. However, the precipitate formed is almost always a basic copper carbonate, such as malachite or azurite, depending on the reaction conditions.
Copper(II) carbonate compounds, particularly the basic carbonates, have various applications. Malachite, for example, has been used as a pigment, in jewelry, and for ornamental purposes. Basic copper carbonates are also used in some fungicides and wood preservatives. In chemistry, they are used in the synthesis of other copper compounds.
The decomposition of copper(II) carbonate or basic copper carbonates upon heating results in the formation of copper(II) oxide (CuO), carbon dioxide (CO2), and water (H2O), in the case of basic carbonates. This reaction is often used in qualitative analysis as a test for the presence of carbonate ions.