Question: how many moles of water in copper sulfate pentahydrate?
Answer: For example, the weight of a mole of CuSO4•5H2O is 250 grams (this is the molar mass of CuSO4•5H2O). A mole of CuSO4•5H2O contains 5 moles of water (which corresponds to 90 grams of water) as part of its structure. Therefore, the substance CuSO4•5H2O always consists of 90/250 or 36% water by weight.