Question

Write the name of the following compound and deduce its molecular mass.

Na₂SO₄

Answer 1

Na₂SO₄ - Sodium sulphate

Molecule	Constituent elements	Atomic mass u	Number of atoms in the molecule	Atomic mass × number of atoms	Mass of the Constituents u
Na2SO4	Na	23	2	23 × 2	46
	S	32	1	32 × 1	32
	O	16	4	16 × 4	64

The molecular mass of Na₂SO₄ = Sum of Constituent atomic masses

(Molecular mass of Na₂SO₄) = (Atomic mass of Na) × 2 + (Atomic mass of S) × 1 + (Atomic mass of O) × 4

= 2 × 23 + 1 × 32 + 4 × 16

= 46 + 32 + 64 

= 142 u