A sample of copper(II) sulfate, CuSO₄, that weighs 2.47 grams picks up
Water from the atmosphere to form a hydrate with the formula CuSO₄ • x H₂O. If the sample weighs 3.86 grams after it picks up water, what is the value of x?

Question

Quizplus · Accepted Answer

The mass of water added to the copper(II) sulfate is the difference between the final and initial masses, which is 3.86 grams - 2.47 grams = 1.39 grams. The molar mass of copper(II) sulfate (CuSO4) is approximately 159.61 g/mol, and the molar mass of water (H2O) is approximately 18.015 g/mol. The moles of CuSO4 in the initial sample is 2.47 grams / 159.61 g/mol ≈ 0.0155 mol. The moles of water added is 1.39 grams / 18.015 g/mol ≈ 0.0772 mol. The ratio of moles of water to moles of CuSO4 is 0.0772 mol / 0.0155 mol ≈ 5, indicating that the value of x, the number of water molecules per formula unit of CuSO4, is 5.

A Sample of Copper(II) Sulfate, CuSO4, That Weighs 2

A Sample of Copper(II) Sulfate, CuSO₄, That Weighs 2