Finding the Percent of a Hydrate - Sample Essay

The purpose of this lab is to apply the principal of percent composition into use. Percent composition is determining the amount of a substance in a compound; either from the formula or experimental data. The purpose of the lab was using percent composition; determine that percent of a hydrate in a anhydrous solution. In the lab we took the hydrous compound cupric sulfate pentahydrate (CuSO4* 5H2O) and decomposed it into its anhydrous form. By using the mass change one can determine the percent of the hydrate.

Hypothesis: For this lab I made two hypothesis’. The first one states that in the CuSO4* 5H2O; a majority of the compound is cupric sulfate rather than the hydrate. The second one states that the NaCl is already a anhydrous compound based on the fact there wasn’t really any significant mass change after heating. Materials and Equipment: 1 hot plate 1 evaporating dish 1 glass stirring rod 1 crucible tongs cupric sulfate pentahydrate (CuSO4* 5H2O) Procedure: (From handout)

1) Find the mass of a clean, dry evaporating dish. 2) Mass out 2. 00g of cupric sulfate pentahydrate in a clean dry evaporating dish. 3) Place evaporating dish on the hot plate and set the hot plate to 7. 4) Hold the evaporating dish steady with crucible tongs while stirring the compounds as it is heated. Try to break up any clumps. Continue heating until the substance has completely changed color. 5) Allow the anhydrous compound to cool. Find the mass of anhydrous powder remaining.

6) Carefully add water drop by drop to the dry powder and record any observations. (Hint: check for temperature change by carefully touching the bottom of the evaporating dish)To find the percent of the hydrate in the CuSO4* 5H2O we subtracted the mass of the hydrous compound from the anhydrous compound to find the approximate mass of H2O. We then divided this number by the hydrous mass and multiplied by 100 to find the percent of the hydrate. To find the moles of CuSO4 we simply divided by the molar mass.