Determination of Percent Water in Compound

Determination of Percent water in Compound AP Chemistry Lab.

The Determination of the Percent Water in a Compound

       I.            Purpose: The purpose of the experiment is to determine the water of hydration of the compound. Also, the chemical formula of the copper (II) sulfate hydrate is determined.

    II.            Pre-Lab Questions:

There were no pre-lab questions.

 III.            Materials: Standard apparatus and equipment, such as crucibles, crucible tongs, and balances were used to conduct the experiment. A sample of copper (II) sulfate with an unknown water of hydration (later discovered to be copper sulfate pentahydrate) was used. A Bunsen burner was used to evaporate the water of hydration from the sample. A desiccator was used to store samples overnight.

 IV.            Procedure: A crucible is weighed with its cover and about 1-1.5 g of the CuSO4 hydrate is added and weighed. The crucible and compound is then gently heated, with the cover slightly tipped. After about 10 minutes, the burner is turned off and allowed to cool for 10 minutes. The crucible is then massed and heated again and allowed to cool again. This process is repeated until the masses measured are within 0.050 g of each other.

    V.            Data: Data is shown in the attached sheet from the lab notebook, and in the table below.

Trial 1

Trial 2

Compound selected for analysis

CuSO4

CuSO4

Mass of crucible and cover (g)

55.0005

41.9758

Mass of crucible, cover, and hydrated sample (g)

56.1115

43.0247

Mass of hydrated sample (g)

1.1110

1.0489

Mass of crucible, cover, and dehydrated sample – 1st weighing (g)

55.6798

43.0053

Mass of crucible, cover, and dehydrated sample – 2nd weighing (g)

55.6744

42.6163

Mass of crucible, cover, and dehydrated sample – 3rd weighing (g)

_

42.6134

Mass of crucible, cover, and dehydrated sample – 4th weighing (g)

_

_

Mass of dehydrated sample (g)

0.6739

0.6376

Mass of water evolved (g)

0.4371

0.4114

Ratio of moles CuSO4 to moles H2O

1 to 5.7

1 to 5.7

 VI.            Calculations and Graphs: 

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