Hydrated compounds are any compounds that have chemically attached water molecules or hydrogen and oxygen atoms. These compounds can dissociate into water and other compounds. Hydrated compounds may be either organic, containing carbon atoms, or inorganic.
An example of an organic hydrate is ethanol, which is also known as ethyl hydrate. The chemical formula is CH3OH.
Inorganic hydrates are often salts and crystals that may change colors when the water molecules are driven off. They may be used as water indicators. An example is cobalt II chloride, which is red when hydrated and blue when not hydrated. The hydrated formula is Co-Cl2.6H20. When the water is removed, the compounds may be called anhydrous.
The number of water molecules attached are noted at the end of the compound formula and by (n) and are read as Greek numbers such as hexahydrate in the cobalt II chloride formula. Compounds with a single water molecule are called monohydrates. Washing soda is a commonly used hydrated compound with the chemical formula Na2So4.10H2O and the name sodium carbonate decahydrate. Other well-known inorganic hydrates include Borax, which is sodium tetra borax decahydrate, Na2B4.10H2O, and Epsom salt, which is magnesium sulfate hepta-hydrate, MgSO4.7H2O.
Some gases may form hydrated compounds called clathrates in which the water molecules form loose frameworks around the gas molecule.