Question

A 1.0 g sample of the hydrate CoSO4 x ?H2O gave on heating, 0.55 g of the anhydrous salt, cobalt (II) sulfate. What is the formula of the hydrate?

Answer 1

Step-by-step explanation:

Molar mass of CoSO4 = 155g/mol

Moles of CoSo4 = 0.55/155 = 0.00354mol.

Molar mass of H2O = 18g/mol

Mass of H2O = 1 - 0.55 = 0.45g

Moles of H2O = 0.45/18 = 0.025mol

Molar ratio of CoSo4 : H2O = 0.00354 : 0.025 ≈ 1 : 7.

Hence, the chemical formula of the hydrated cobalt (II) salt is CoSO4 • 7 H2O.