Synthesis

SynthesisCopper(II) hydroxide can be produced by adding a small amount of sodium hydroxide to a dilute solution of copper(II) sulfate (CuSO4 5H2O). The precipitate produced in this manner, however, often contains water molecules and an appreciable amount of sodium hydroxide impurity. A purer product can be attained if ammonium chloride is added to the solution beforehand. Nevertheless, it is impossible to obtain a pure product; processes for eliminating impurities lead to the destruction of the hydroxide, giving rise to the more stable oxide, CuO.[5] Alternatively, copper hydroxide is readily made by electrolysis of water (containing a little electrolyte such as sodium bicarbonate). A copper anode is used, often made from scrap copper.

"Copper in moist air slowly acquires a dull green coating. The green material is a 1:1 mole mixture of Cu(OH)2 and CuCO3."[6]2 Cu (s) + H2O (g) + CO2 (g) + O2 (g) Cu(OH)2 (s) + CuCO3 (s)

This is the patina that forms on bronze and other copper alloy statues such as the Statue of Liberty.

[edit] ReactionsMoist samples of copper(II) hydroxide slowly turn black due to the formation of copper(II) oxide.[7] When it is dry, however, copper(II) hydroxide does not decompose unless it is heated to 185C.[8]Copper(II) hydroxide reacts with a solution of ammonia to form a deep blue solution consisting of the [Cu(NH3)4]2+ complex ion, but the hydroxide is reformed when the solution is diluted with water. Copper(II) hydroxide in ammonia solution, known as Schweizer's reagent, possesses the interesting ability to dissolve cellulose. This property led to it being used in the production of rayon, a cellulose fiber.

Since copper(II) hydroxide is mildly amphoteric, it dissolves slightly in concentrated alkali, forming [Cu(OH)4]2-.[9]