The answer to this question has to be with the task that is the salt during hydration makes a hydrate, you have to see it as a compound complex has been produced, then the water molecules are ligands joined together to the central cation and according with the type of compound formed it could be paramagnetic or not, better try to find the theory about complex compounds that usually make the transition metals with ligands like water that contain unpaired electrons that are introduced in the "d" orbitals free.

Basically hydration will modify your possible exchange pathways, so you have to take into consideration the new structure, to see how it affects the magnetic properties of the compound.