Epsom salt, a common hydrate, has the formula shown below. If I measure out 125 g of epsom salt to add to my foot soak, what mass of the epsom salt is H2O?

Answer:
The answer to your question is 64.02 g of H₂O
Explanation:
Data
Mass of magnesium sulfate hepta hydrated = 125 g
Mass of water = ?
Process
1.- Calculate the molar mass of the salt and the molar mass of water
molar mass of MgSO₄ 7H₂O = 24 + 32 + 64 + 14 + 112 = 246 g
mass of H₂O = 2 + 16 = 18 g
2.- Use proportions to calculate the mass of water in the epsom salt
246 g MgSO₄ 7H₂O------------------------- 126 g of H₂O
125 g ------------------------- x
x = (125 x 126)/246
x = 15750/246
x = 64.02 g of H₂O