Is the reaction between magnesium sulfate and water endothermic or exothermic?

The reaction ofanhydrousmagnesium sulfate with water is exothermic. This is a fine white powder. The container must be covered for it will react with water in the air if exposed. The container will feel warm otherwise. In the tests I've done, it gets no higher than 30˚C which is roughly 86˚F. So it is warm, but not hot.

The hydrous magnesium sulfate (epsom salt) is endothermic. This is a crystalized form magnesium sulfate where water is used in thecrystalbonds. To access the magnesium sulfate in its ionized form, the crystal must be broken. This requires energy and thus results in a lower heat yield in he aqueous solution.