Caffeine Lab Handout
Lab Report
Calculate % recovery of caffeine from the tea leaves (show your calculations). Make sure all of the
masses you collected during the lab are in a table. Show all of your calculations. Discuss the steps of the
lab procedure where you may have “lost” caffeine (see post-lab Q1 below)…you probably didn’t recover
all of the caffeine. Give 3 specific steps during the procedure where caffeine could have been “lost”
and how could you improve the amount your recovered (these will be your sources of error).
Post Lab Questions
1. No matter how carefully you perform this lab, your percent recovery will always be a low
number (even if you recovered all of the caffeine from the leavers). Explain why.
2. The Lipton Tea box lists 55mg of caffeine is contained in each tea bag. Calculate the % of this
you recovered based on your post-sublimation mass of caffeine.
3. Based on the structure of caffeine, would you expect it to act as a base or an acid when
dissolved in water? Explain.
4. A student starts with a compound in an aqueous solution. An organic solvent is then mixed with
the aqueous solution in a container then agitated. After this step, there are two immiscible
layers: an aqueous layer and an organic layer. 80% of the compound is now dissolved in the
organic layer while only 20% remains in the aqueous layer. Give an explanation as to why more
of the compound was in the organic layer.
5. If you removed the organic layer, and then did a second extraction with the same amount of
organic solvent as you used in your first extraction, would you be able to remove the rest (all) of
compound from aqueous solution with the second extraction? Explain. (Hint: extraction is an
equilibrium process).
EXTRA CREDIT (1.5 points) Using the information from both questions 3 and 4, calculate the
total % of the compound you could theoretically extract from the aqueous layer after the two
extractions.
6. For a substance that is consumed on a daily basis and is found in many foods, caffeine has a
rather low LD50 of ≈ 200 mg/Kg. Assuming 1lb = 454g, calculate the grams of caffeine you would
need to ingest to reach the LD50. Please show you work.
7. Assuming a can of coke has 34.5mg of caffeine, how many cans of Coke would you have to drink
in one sitting to reach the LD50? Please show you work.
8. After making an aqueous tea solution, a student placed concentrated HCl into the container.
The following was formed:

Explain how the solubility of this form of caffeine would be different in H2O compared to regular
caffeine.

Explain how the solubility of this form of caffeine would be different in methylene chloride
(dichloromethane), CH2Cl2, compared to regular caffeine.
O
(Hint: Both of these questions are about IMF’s. Think about the IMF’s involved)