Question

During heating of hydrated copper (II) sulphate crystals, the following readings were obtained:-
Mass of evaporating dish = 300g
Mass of evaporating dish + hydrated salt = 305g
Mass of evaporating dish + dehydrated salt = 303.2g
Calculate the empirical formula of hydrated copper (II) sulphate.
(Cu = 64.5, S = 32.0, O= 16.0, H = 1)

Answer 1

Empirical formula
Compounds present : CuSO₄ : nH₂O
Mass present                 3.2  :   1.8
R.F.M                          160.5 :  18
No of moles          ^3.2/_160.5    :   ^1.8/₁₈
                                    0.02 : 0.1
Mole ratio              ^0.02/_0.02 : ^0.1/_0.02
                                         1 : 5
E.F. CuSO₄ .5H₂O