A student analyzing 2.000g of Epsom Salt found that it contained 39.0% by mass water. What is the hydration number for this sample?
g epsom salt = 2.00 x 0.61 = 1.22g MgSO4.
g H2O = 2 x 0.39 = 0.78
mols MgSO4 = 1.22/120.4 =0.0101
mols H2O = 0.78/18 = 0.0433
Now find the ratio H2O molecules to 1 molecule of MgSO4.
0.0101/0.0101 = 1.00
0.0433/0.0101 = 4.29
Actually, that 0.29 is too much to throw away and I would not accept such results. The experiment should be done over. I suppose the answer to this problem is MgSO4.4H2O but that's iffy.