What are the procedures on how to separate copper II sulfate from pentahydrate?

Answer 1

1. Thoroughly heat your crucible and allow it to cool on the clay triangle. Then weigh your crucible. This ensures that it is clean and dry.
2. Obtain about 1 g of CuSO4·5H2O in your crucible and weigh it, recording the mass to the maximum available precision.
3. Make a prediction about the amount of mass that will be lost when you heat the sample of copper (II) sulfate pentahydrate. Specifically, calculate the mass of the anhydrous salt and the mass of water that will be driven off. Show this to your instructor before proceeding.
4. Once you have your instructor's approval, place the crucible containing the CuSO4·5H2O on the clay triangle.
5. Light the bunsen burner and adjust for a hot flame.
6. Heat the crucible as gently as possible with the burner by moving the burner under the crucible for a few seconds at a time. Note the release of any steam from the crucible.
7. Remove the heat source and use a pair of lab spatulas to occasionally stir the copper sulfate. Carefully scrape all of it back into the crucible. Be careful not to do this while heating!
8. Continue heating gently until the salt turns completely white. Be careful not to overheat! The heat can become so intense that the sulfate in the salt begins to break down. If this happens the salt will turn yellow and produce a sulfurous smell. It will also ruin your data since it will reduce the mass more than expected due to the decomposition of the salt.
9. Stop heating when the salt has lost all traces of blue color. Allow the crucible and its contents to cool completely.
10. Once the crucible is cool, find its mass. Then stir the copper(II) sulfate and heat the crucible and its contents again for a short time. Then allow it to cool and weigh it. If the mass is the same as the previous weighing, then the salt has been completely dehydrated. If not, repeat the heating/cooling/weighing process until two successive weighings have the same mass.
11. Record the final mass of the anhydrous salt in you lab notebook and do the calculations to show that the molar ratio of water to anhydrous salt really is 5:1.
12. Empty the anhydrous salt onto a large watch glass. Use the dropper to add a very little water to the anhydrous copper (II) sulfate. Describe what happens in your lab notebook. For your report think about what is happening at the molecular level when you add water. Draw a model.
13. When you finished this part of the lab empty the re-hydrated CuSO4·5H2O into the beaker provided by your instructor for this purpose. Then begin Part II.

Part II

In this part of the lab you will repeat the same procedure performed for the salt of known formula with a salt for which you do not know the hydrate formula. The salt is magnesium sulfate (MgSO4). Your correct identification of the hydrate formula is worth 5 points on your lab report. To ensure better chances of getting the correct result you may want to consider doing at least two (and perhaps three) trials. For each trial use a minimum of 2 g. The magnesium sulfate is not nearly so hazardous as the copper (II) sulfate and a larger amount will help to reduce errors due to small lab balance inaccuracies. An additional challenge is that both the hydrate and anhydrous salt are white. Finally, unless you frequently stop heating to stir the crystals they will combine and harden, possibly trapping water inside.

By the way, magnesium sulfate is the chemical name for Epsom Salts. Epsom Salts were discovered by a farmer in Epsom, England. Every day his cows waded through water containing naturally high amounts of magnesium sulfate. He found that the cows showed evidence of diarrhea but also that the incidence of small wounds near their hooves was reduced. Epsom Salts are used as a laxative and in foot soaks and bath salts. It soothes tired muscles and can help to heal skin problems, including acne.