Formula of a Hydrate Lab

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Hydrates are compound with a constant composition. Concepts of Law of Definite Proportions (hydrates remain in constant proportions) and Law of Conservation of Mass (this idea is used to determine the mass of water in the compound and, subsequently, the formula of the compound) are expressed in this experiment. In this experiment, the goal was to find the formula of copper sulfate pentahydrate by heating a sample of the blue compound in order to evaporate the water and receive the white-colored copper sulfate anhydrous. Using the mass of the original sample of copper sulfate pentahydrate subtracted by the new mass of the copper sulfate anhydrous, the mass of water lost is obtained and used to find the empirical formula. The expectation for the empirical formula was CuSO4 * 5H2O.


1.Set up ring and Bunsen burner
2.Weigh crucible
3.Weigh crucible and hydrate
4.Crush hydrate
5.Add hydrate to the crucible
6.Weigh crushed hydrate
7.Light Bunsen burner
8.Adjust ring stand and heat the hydrate until it turns white/gray 9.Cool then weigh the crucible

Mass of crucible 23.15 grams
Mass of Crucible with crushed hydrate29.62 grams
Mass of crushed hydrate6.47 grams
Mass of crucible with crushed hydrate after heating26.64 grams Mass of crushed hydrate after heating3.49 grams

Therefore, mass of Water that has escaped = (mass of crushed hydrate) - (mass of crushed hydrate after heating) Mass of H2O = 2.98 grams
Therefore mols of H2O = (2.98g) * (1mol)\(18g) = .165 mols H2O So, mols of Cu2SO4 = (3.49g) * (1mol)\(223.15g) = .015 mols Cu2SO4

Divide by .015
Common ratio:
Cu2SO4 = 1
H2O = 10
Therefore, empirical formula of Cu2SO4 . H2O should be: Cu2SO4 . 10H2O

A hydrate is a substance that holds water in a certain ratio. As Hydrates are compounds with constant composition, we were able to easily determine this ratio by evaporating the water and then calculating a common ratio. We had...
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