Answer:
0.369 moles of H₂O.
Explanation:
The molar mass of the hydrate salt is equal to the molar mass of the anhydrous salt plus the molar mass of water times the moles of water.
M(MgSO₄·7H₂O) = M(MgSO₄) + 7 × M(H₂O)
M(MgSO₄·7H₂O) = 168 g/mol + 7 × 18 g/mol
M(MgSO₄·7H₂O) = 294 g/mol
Every 294 g of MgSO₄·7H₂O there are 126 g of H₂O. So, for 15.5 g of MgSO₄·7H₂O,
[tex]15.5gMgSO_{4}.7H_{2}O.\frac{126gH_{2}O}{294gMgSO_{4}.7H_{2}O} .\frac{1molH_{2}O}{18gH_{2}O}=0.369mol H_{2}O[/tex]
