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.