Question: how to find moles of water in a sample?
Answer: Divide the mass of water by the molar mass of water to get moles of water. 2.60 g H2 O / (18.00 g/mol H2 O) = 0.144 moles H2 O. Divide the mass of anhydrate by the molar mass of anhydrate to get moles of anhydrate.