A hydrate of copper(II) chloride has the following formula (CuCl2 * x H2O):

Question

A hydrate of copper(II) chloride has the following formula (CuCl2  x H2O):  The water in a 3.41-g sample of the hydrate was driven off by heating. The remaining sample had a mass of 2.69 g .

Find the number of waters of hydration (x) in the hydrate.

Answer 1

Mass of water = 3.41 g - 2.69 g = 0.72 g

moles H2O = 0.72 g H2O x 1 mol H2O/18 g = 0.04 moles H2O

moles CuCl2 = 2.69 g x 1 mol CuCl2/134 g = 0.02 moles CuCl2

mole ratio CuCl2 : H2O = 1 : 2

Number of waters of hydration = 2

CuCl₂ • 2H₂O