# Formula of a Hydrate

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AP Chemistry P2 Experiment 2: Formula of a Hydrate 9/24/2013 Purpose: Calculate the percent composition of water in a hydrate and determine the empirical formula of the hydrate. Procedure: 1) Set up ring stand with ring clamp, clay triangle, crucible with lid, and burner. Adjust the height of the ring stand. 2) Dehydrating Procedures: 3. Measure approximately 1 g of Copper(II) Sulfate Hydrate into the crucible and crucible and lid. 4. Heat the crucible gently. 5. Stirring carefully and observe the color of the hydrate until it changes to a consistent white color, then the Copper(II) Sulfate is dehydrated. 6. Turn off the burner, and wait to cool down the material. 7. Carefully determine the mass of the Copper(II) Sulfate, crucible, and lid. 8. Obtain the accepted percent (by mass) composition of water. Pre-Lab Questions 1. Hydrates are crystal solids and water. 2. In order to determine the percent composition and the empirical formula of a hydrate, you must know how much water is in the hydrate. As you cannot measure the mass of the water as it gets added to the salt, how can you determine this? By dehydrating it using fire. The contrast mass between pure solid and solid with water gives the mass of water. 3. What is the formula for copper(II) sulfate? CuSO4 4. What is the molar mass for anhydrous (without water) copper(II) sulfate? 159.62 g/mol Result: Observation: Some gray white substances precipitated from the water in the crucible. Data: * Mass of purified crucible and lid 30.59g * Mass of crucible and lid and hydrate 31.57g * Mass of hydrate alone 31.57g- 30.59g = .98g * Mass of crucible and lid and dehydrate 31.11g * Mass of dehydrate alone .52g This lab shows that hydrates are made up of crystal solids and water,