Given that the molar mass of Na2SO4 * nH2O is 322.1 g/mol calculate the number of moles of water in this hydrate

The molar mass of anhydrous Na₂SO₄ = [2 (23) + 32 + 4 (16) ]

= 142 g/mol

If the molar mass of hydrated Na₂SO₄ = 322 g/mol

Since hydrated salt = Anhydrous Salt + Water

Then the mass of hydration (Water) = 322 g/mol - 142 g/mol

= 180 g/mol

Since the molar mass of water itself is 18 g/mol

⇒ Moles of water = 180 g/mol : 18g/mol

= 10

Thus n = 10; the formula of the hydrated salt is Na₂SO₄ · 10H₂O (Sodium Sulphate Decahydrate)