Question

A 1.50-g sample of hydrated copper(II) sulfate was heated carefully until it had changed completely to anhydrous copper(II) sulfate () with a mass of 0.957 g. Determine the value of x. [This number is called the number of waters of hydration of copper(II) sulfate. It specifies the number of water molecules per formula unit of in the hydrated crystal.]

Answer 1

X = 5

Step-by-step explanation:

Total mass here is 1.5g. Now after heating we have a mass of 0.957g Cu. This means heating had caused a loss of 1.5 - 0.957 = 0.543g of water.

Now, we will try to convert this into moles. This can be done by dividing the respective masses by the molar masses. While the mass of water is 18g/mol, the molar mass of CuSO4 is 160g/mol.

The division of the respective masses by the molar masses is thus:

CuSO4 = 0.957/160 = 0.006 moles

H2O = 0.543/18 = 0.03 moles

The ratios of the moles is thus: 0.03/0.006 = 5

Hence, the number of molecules of water of crystallization is 5

This means x = 5