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Difficulty: EasyRelative Atomic Mass, Relative Molecular Mass, and Carbon-12 Scale

Calculate the relative molecular mass of hydrated magnesium tetraoxosulfate(VI), MgSO4⋅7H2OMgSO_4 \cdot 7H_2O. [Mg=24,S=32,O=16,H=1][Mg = 24, S = 32, O = 16, H = 1]

Answer: 246

Answer

246
The relative molecular mass of MgSO4⋅7H2OMgSO_4 \cdot 7H_2O is calculated by summing the atomic masses of all constituent atoms. The anhydrous part MgSO4MgSO_4 contributes 24+32+(4×16)=12024 + 32 + (4 \times 16) = 120. The water of crystallization 7H2O7H_2O contributes 7×(2+16)=1267 \times (2 + 16) = 126. The total relative molecular mass is 120+126=246120 + 126 = 246.

Step-by-Step Solution

1
Calculate the mass of the anhydrous salt component, MgSO4MgSO_4
24+32+(4×16)=12024 + 32 + (4 \times 16) = 120
Sum the relative atomic masses of one magnesium atom, one sulfur atom, and four oxygen atoms.
2
Calculate the mass of the water of crystallization component, 7H2O7H_2O
7×(2+16)=1267 \times (2 + 16) = 126
Multiply the molecular mass of one water molecule (18) by the coefficient 7.
3
Combine the mass of MgSO4MgSO_4 and 7H2O7H_2O
120+126=246120 + 126 = 246
The total relative molecular mass of a hydrated salt is the sum of the anhydrous salt mass and the water of crystallization mass.

Key Concept

Relative Molecular Mass of Hydrated Salts
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Topics

Relative Atomic Mass, Relative Molecular Mass, and Carbon-12 Scale

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