Copper(II) nitrate trihydrate is a blue crystalline compound with the chemical formula Cu(NO₃)₂·3H₂O. It consists of one copper ion, two nitrate ions, and three water molecules. This compound is commonly used in laboratories and various industrial applications, including as a catalyst and in the production of other copper compounds. When heated, copper(II) nitrate trihydrate decomposes, releasing nitrogen dioxide and oxygen gases. It is soluble in water, making it useful in aqueous solutions for experiments and reactions. Safety precautions should be taken when handling this compound, as it can be harmful if ingested or inhaled.