# Calculate the molar mass of the following compounds:(i) MgO (ii) Na2CO3(iii) H3PO4 (iv) Ca(OH)2(v) Al2(SO4)3

i. MgO:

Molar mass of Mg + 2 × Molar mass of oxygen

24u + 2×16

24 + 32

56g/mol
Thus, the molar mass of MgO is 56g/mol.

ii. Na2CO3:

2 × Molar mass of Na + Molar mass of carbon + 3×molar mass of oxygen

2 × 23 + 12 + 3 × 16

46 + 12 + 48

106g/mol

Thus, the molar mass of Na2CO3 is 106g/mol.

iii. H3PO4:

3 × Molar mass of hydrogen + Molar mass of phosphorus + 4×molar mass of oxygen

3 × 1 + 31 + 4 × 16

3 + 31 + 64

98g/mol

Thus, the molar mass of H3PO4 is 98g/mol.

iv. Ca(OH)2

Molar mass of calcium + 2 × Molar mass of oxygen + 2×molar mass of hydrogen

40 + 2 × 16 + 2 × 1

40 + 32 + 2

74g/mol

Thus, the molar mass of Ca(OH)2 is 74g/mol.

v. Al2(SO4)3

2 × Molar mass of aluminium + 3 × Molar mass of sulphur + 12×molar mass of oxygen

2 × 27 + 3 × 32 + 12 × 16

54 + 96 + 192

342g/mol

Thus, the molar mass of Al2(SO4)is 342g/mol.

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