What reaction is called a hydration reaction? What compounds are called hydrates? Give examples of known hydrates.

Hydration is the attachment of water molecules to molecules or ions.
Hydrates are products of the addition of water to inorganic and organic substances. If the hydrate is crystalline; then it is called crystalline hydrate. An example of hydrates: CuSO4 * 5H2O (copper sulfate), H2SO4 * H2O (sulfuric acid hydrate).

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