What is the answer to this question?
Copper nitrate is an attractive blue-green inorganic salt. It finds many uses, including pyrotechnics and chemical voltaic cell reactions. It is also used as a corrosion inhibitor and to produce copper oxide.
Soluble in water
Unlike nitric acid, which is very soluble, copper nitrate displaces water from the Cu+ ion. This is because the OH- ion binds to the Cu+ ion even more strongly than does water, which causes the copper ion to be replaced by hydroxide. The resulting blue precipitate, Cu(OH)2, is then oxidized by zinc metal, producing copper oxide, CuO.
Hydrated form
Anhydrous copper nitrate is a deep-blue-green, crystalline solid. It is commonly used in school laboratories to demonstrate chemical voltaic cell reactions.
In this demonstration, we will use hydrated copper nitrate, which is much more common than anhydrous, and which can be purchased from most chemical suppliers. We will mix the hydrated crystals with water and stir. In a short time, most of the hydrates will dissolve and the water will become pale blue.
The hydrates will be hygroscopic and will turn into at least 5 different hydrated forms as the water is absorbed. When the hydrates are removed from the solution, it will decompose to copper oxide and nitrogen dioxide gas.
Hydrated copper nitrate is easy to prepare. It is readily available in a variety of powder and spherical forms from most chemical suppliers. In addition, the hydrates can be prepared by adding concentrated nitric acid to the anhydrous solution and then drying the solution. The hydrates can be re-precipitated as needed, and can be stored at room temperature or slightly higher, to keep them from decomposing.