J.R. S. answered 08/23/24
Ph.D. University Professor with 10+ years Tutoring Experience
mass of CuSO4•XH2O (hydrate) = 21.66 g - 20.15 g = 1.51 g
mass of H2O lost/present = 21.66 g - 21.13 g = 0.53 g
mass of CuSO4 (dehydrate; anhydrous) = 1.51g - 0.53 g = 0.98 g
molar mass CuSO4 = 159.60 g/mole
molar mass H2O = 18.02 g/mole
moles CuSO4 (dehydrate; anhydrous) present = 0.98 g x 1 mol / 159.60 g = 6.140x10-3 moles
moles H2O lost/present = 0.53 g x 1 mol / 18.02 g = 0.0294 moles
How many moles of H2O are present per mole of CuSO4?
0.0294 moles H2O / 6.140x10-3 moles CuSO4 = 4.8 ~ 5 moles H2O per mole of CuSO4
Formula of the original hydrate = CuSO4•5H2O