48 g of magnesium sulfate are left after dehydration of magnesium sulfate heptahydrate . What was the original weight of the sample before dehydration?

98.6g is the mass of the heptahydrate

Explanation:

The hydrated magnesium sulfate contains 7 moles of water per mole of magnesium sulfate. 1 mole of MgSO₄ dehydrated is 1 mole of MgSO₄.7H₂O

To solve this question we must find the moles of MgSO₄. These moles = Moles of MgSO₄.7H₂O. Then, we must convert the moles to mass:

Moles MgSO₄ -Molar mass: 120.366g/mol-:

48g * (1mol / 120.366g) = 0.40 moles MgSO₄ = moles MgSO₄.7H₂O

Mass MgSO₄.7H₂O -Molar  mass: 246.47456 g/mol-:

0.40 moles MgSO₄.7H₂O * (246.47456 g / 1mol) =

98.6g is the mass of the heptahydrate

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