Say you had copper(II) sulfate pentahydrate as a solid.

In an aqueous solution, is it still referred to by its hydrated form? Is it still called copper(II) sulfate pentahydrate (aqueous) or simply copper (II) sulfate (aqueous)?

I guess what I'm asking here is does the "hydrate" label apply exclusively to solids?

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    $\begingroup$ Yes, the "hydrate" label applies exclusively to solids. Once you got your salt dissolved, there is absolutely nothing special about those water molecules that came from the solid. $\endgroup$ – Ivan Neretin Oct 11 '15 at 17:01

Yes, the ‘hydrate’ label applies exclusively to solids. Consider the following experiment: Dissolve both anhydrous $\ce{CuSO4}$ and $\ce{CuSO4 . 5 H2O}$ in water. You will get the same, blue solution.

What happened on a microscopic level is that the crystal lattice which once included the water atoms is broken up and the ions dissolve separately. What used to be copper(II) sulphate pentahydrate is now turned into a hexaaquacopper(II) complex.

$$\ce{CuSO4.5 H2O + H2O -> [Cu(H2O)6]^2+ + SO4^{2-}_{~(aq)}}$$


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