Question: how many molecules of water of crystallisation are present in one molecule of copper sulphate?
Answer: So, one molecule of copper sulphate in the lattice has 5 molecules of water associated with it. This is true for nearly all of the molecules. To summarize, most of the crystal's molecules have water with them, on average. Hence in one mole, you'll have on average 6.023 x 10^23 molecules with water.