Question: what is the empirical formula of copper sulfate hydrate?
Answer: These compounds are called hydrates. Copper(II) sulfate pentahydrate is an example of such a hydrate. Its formula is CuSO4 5H2O. The five in front of the formula for water tells us there are 5 water molecules per formula unit of CuSO4 (or 5 moles of water per mole of CuSO4).