What is the percent by mass of magnesium sulfate in cap m g cap s cap o sub 4 ⋅ 7 cap h sub 2 cap o ? Use percent Element is equal to total mass of element in compound over molar mass of compound times 100

Find the molar mass of MgSO₄ and divide it by the molar mass of the entire hydrate. MgSO₄ has a molar mass of about 120.37 g/mol, while MgSO₄·7H₂O has a molar mass of 120.37 + 7(18.02) = 246.49 g/mol. Thus, the percent by mass of magnesium sulfate is (120.37 ÷ 246.49) × 100 ≈ 48.83%, choice A.

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