Module 1: Assigned Problems Chemical Separation and Purification; Part I

The module quiz and mid-term exam for this course will consist of problems similar to those assigned below. You should do as many of these problems as you need to in order to be confident that you will be able to perform well on a quiz or an exam.

Please answer the following questions concerning Chemical Separation and Purification.

1. The distribution coefficient between hexanes and water for solute B is 7.5. What weight of B would be removed from a solution of 5.00 g of B in 50 mL of water by a single extraction with 50 mL of hexanes?a. 4.4 gb. 0.6 gc. 5.0 gd. 3.3 g

2. How much of solute B would have been removed by four successive extractions with 12.5 mL portions of hexanes.a. 3.26 gb. 1.74 gc. 2.44 gd. 4.9 g

3. Will charged molecules be more or less soluble in the organic phase of an extraction?

4. A mixture of sand, aniline, and naphthalene in ether is best separated bya. filtration, followed by acidic extraction, followed by recrystallization.b. filtration, followed by basic extraction, followed by recrystallization.c. extraction, followed by sublimation, followed by GC.d. filtration, followed by centrifugation, followed by extraction.

5. Which one of the following compounds would be the most effective in extracting benzoic acid from a diethyl ether solution? a. Tetrahydrofuranb. Aqueous sodium hydroxidec. Aqueous hydrochloric acidd. Water

6. Centrifugation is generally used to separate big things from each other at different rates depending upon their mass, their density, and their shape. Do you think centrifugation is a good technique to separate the components of blood from plasma? The components of blood include red blood cells, white blood cells, and platelets.

7. To make a solid sublime, you musta. lower the temperature and raise the pressure.b. raise the pressure and the temperature.c. raise the temperature and lower the pressure.d. run the sublimation at normal pressure and at room temperature.

8. Why is fluted filter paper more commonly used than the usual filter cone?

9. Describe the characteristics of a good recrystallization solvent.

10. Fractional distillation would most likely be used to separate which of the following solutions?a. Methylene chloride (bp 41°C) and water (bp 100°C)b. Ethyl acetates (bp 77°C) and ethanol (bp 80°C)c. Aniline (bp 184°C) and benzyl alcohol (bp 22°C)d. Aniline (bp 184°C) and water (bp 100°C)

11. Which of the following statements account for the fact that dimethyl sulfoxide is miscible in water, where as dimethyl sulfide is not?

a. Dimethyl sulfoxide is a non-polar compound that rapidly penetrates the skin.b. Dimethyl sulfide is symmetrical, which causes it to develop a dipole moment.c. Dimethyl sulfide has a low boiling point and density issues prevent it from being water soluble.d. Dimethyl sulfoxide is a polar compound.

12. What is the function of Na2SO4, sodium sulfate, when it is added to an organic solvent?a. It facilitates the reaction between the solute and the solvent.b. It facilitates the separation between the solute and the solvent.c. It removes the impurities of the solution.d. It acts as a drying agent.