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.
