Hydrated salt

When a hydrated salt is dissolved in water, the water of crystallization is NOT removed but becomes part of the solvent.

The hydrated salt contains cations, anions and water of crystallization. When the hydrated salt is dissolved in water, all the cations, anions and water of crystallization separate and become mobile ions (i.e. the cations and anions) or mobile molecules (i.e. water molecules). The mobile water molecules become part of the solvent, and it is impossible to distinguish whether a water molecule in the solution originally is a solvent molecule or a molecule of water of crystallization.