Question

as a solution of copper sulfate slowly evaporates, beautiful blue crystals made of cu(ii) and sulfate ions form such that water molecules are trapped inside the crystals. the overall formula of the compound is cuso4 • 5h2o.

Answer 1

There are five molecules of the water of crystallization.

Mass of hydrated copper(II) sulfate CuSO4 · xH2O = 0.755 g

Mass of anhydrous copper(II) sulfate CuSO4 = 0.483 g

Molar mass of hydrated copper(II) sulfate CuSO4 · xH2O = (160 + 18x) g/mol

Molar mass of anhydrous copper(II) sulfate CuSO4 =160 g/mol

Number of moles of hydrated copper(II) sulfate CuSO4 · xH2O = Number of moles of anhydrous copper(II) sulfate CuSO4

Therefore;

0.755 g/(160 + 18x) g/mol = 0.483 g/160 g/mol

0.755 * 160 = 0.483 (160 + 18x)

120.8 = 77.28 * 8.694x

120.8 - 77.28 = 8.694x

x = (120.8 - 77.28)/8.694

x = 5

The formula of the hydrated salt is CuSO4 · 5H2O.