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?

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.

in the given question, the partial pressure is calculated by using the ideal gas equation, that is, pv = nrt

here, p is pressure, v is volume = 25 l, n is number of moles = 0.0104 moles, r is gas constant = -0.0821 l.atm / mol.k

t is temperature = 273 k

p = nrt / v

p = (0.0104 mol × 0.0821 l.atm / mol.k × 273 k) / 25 l

= 0.0093 atm