Name: ______Hydrate Lab

Purpose: To determine the number of moles of water (x) in one mole of an unknown hydrate. (CuSO4.xH2O)

Materials: Burner, matches, crucibles and covers, ring stand, ring, clay triangle, balance, tongs, hydrate.

Pre-lab Questions:

1. Define the term hydrate and explain how it is different than an anhydrate.

2. What is the basic formula of the hydrate and the anhydrate in this lab?

3. Calculate the molar mass of CuSO4 (the anhydrate).

4. Write a scientific explanation to either agree or disagree with the following statement made by a former

student: “All students will have a different percent of water in their hydrate because they will use

different amount of hydrate at the beginning of the lab.”

Claim: ______

______

Evidence: ______

______

Reasoning: ______

______

Procedure:

1.  Obtain and clean a crucible and cover. Place the crucible and cover on a clay triangle supported by a ring on a ring stand and place the cover on slightly off center.

2.  Dry the crucible with towel and then for approximately 3 minutes over a burner flame.

3.  Turn off the burner and allow the crucible and cover to cool for one minute. Using tongs transport the crucible and cover to a balance. Record the mass of the cool crucible and cover.

Mass of crucible and cover: ______

4.  Add between 1-2 grams of the unknown hydrate to the crucible and record the actual mass of the crucible, hydrate and cover. Place the crucible and contents with cover on the triangle with the cover off centered.

Mass of crucible, cover, and Hydrate: ______

5.  Heat the crucible gently in the flame for 10 minutes. Do not allow the crucible to turn red.

6.  Let the crucible and cover cool for one minute. Then, using tongs mass the crucible, cover and contents.

Mass of crucible, cover, and product #1: ______

7.  Re-heat the sample for one minute, cool and re-mass. Repeat this step until the mass remains constant.

Mass of crucible, cover, and product #2: ______

Mass of crucible, cover, and product #3: ______

8.  Record observations about the hydrate before and after heating:

Questions: SHOW ALL WORK!!! (With units and sigfigs.)

1.  Using YOUR DATA calculate the percent of water in your hydrate.

  1. Find the mass of the hydrate CuSO4.xH2O.
  1. Find the mass of the anhydrate CuSO4
  1. Find the mass of water lost.
  1. Calculate the percent of water in the hydrate.
  1. Compare your percent water in the hydrate with another group. Are they within 5% of each other? Compare this result to your hypothesis from the pre-lab questions.

2.  Using YOUR DATA determine the chemical formula of the hydrate you used:

  1. Convert the mass of the anhydrate CuSO4 to moles.
  1. Convert the mass of water to moles.
  1. Divide the moles of water by the moles of anhydrate to find a whole number. This is the value of x in the CuSO4.xH2O.

3.  The hydrate should be CuSO4.5H2O. Calculate the true percent of water in the hydrate.

4.  Calculate your percent error.

5.  What was the purpose of heating the hydrate more than once?

6.  If a student weighed the hydrate and then accidentally lost a small amount before heating the hydrate, how would that affect the percent of water in the hydrate?