Answered: What does it mean for two solvents to…

Chemistry

10th Edition

ISBN:9781305957404

Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Chapter1: Chemical Foundations

Section: Chapter Questions

Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...

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Extraction of Caffeine Post-lab

4. What does it mean for two solvents to be immiscible?

5. On the report sheet, you calculated your percent recovery of caffeine.

a. If your percent was less than 90%, give at least one reason why it was less.

b. A group of students have their percent yield more than 100%, give at least one reason
why it was more than 100%. Do NOT simply say “human error.” Be specific about the types
of errors (human or otherwise) that may have occurred, leading to a recovery more than eor
equal to 100% (Is this possible Why?)

6. Based on what you observed during this experiment, is dichloromethane denser OR less
dense than water? Explain your reasoning.

7. Based on what happened in this experiment, is caffeine more soluble in water OR more
soluble in dichloromethane? Explain your reasoning.

8. Ethanol is miscible with water. (After all, alcoholic beverages don t separate into an “alcohol‟
layer” and a “water layer.”) Assuming that caffeine is soluble in ethanol, could you use
ethanol as a solvent to extract caffeine from coffee (rather than using dichloromethane as
the extraction solvent)? Explain why or why not.

9. A 12 oz can of Coke contains 46 mg of caffeine. One fluid ounce is equivalent to 29.57 mL
(1 oz = 29.57 mL). What is the concentration of caffeine in Coke, in units of mg/mL? Show
your work.

10. What is an alkaloid?

11. Why is anhydrous sodium carbonate used in isolation of Caffeine? What do you
think would happen if we used it during our simulation?

12. Why caffeine has 178oC as point of sublimation but 237oC as melting point? How
can you find the melting point of caffeine?

13. What should you do if there is a question about which layer is the organic one
during an extraction procedure?

14. How do you know you have the right compound? Comment on the test you
have done or would have done in order to determine your product is the
right compound.

15. Why did you consider the lower layer as organic layer in the extraction phase
between water and methylene chloride. If you do not have access to data, how will
you determine which layer is organic and which is aqueous.

16. List the advantages and disadvantages List the advantages and disadvantages of
sublimation as a purification technique.

This is all part of one question. Thank you so much!

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