Practice Problems for Exam 2
Practice Problems for Exam 2 Chem 241
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This 4 page Bundle was uploaded by Chelsea Nebolisa on Tuesday March 1, 2016. The Bundle belongs to Chem 241 at University of North Carolina - Chapel Hill taught by Dr. Tiani in Spring 2016. Since its upload, it has received 36 views. For similar materials see Analytical in Chemistry at University of North Carolina - Chapel Hill.
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Date Created: 03/01/16
1. An open tubular gas chromatography column is 35.7 m long and has an inner diameter of 0.250 mm. It is coated on the inside wall with a layer of stationary phase that is 1.8 µm (0.0018 mm) thick. Unretained solute, methane, passes through in 6.39 min, whereas toluene has a retention time of 16.35 min. 2. Listed in the table of chromatographic data below are the retention times and peak widths for a chromatographic separation carried out on a 10.0 cm column. Calculate the plate height, in millimeters, for pyrene. Compound Time (min) Width 1/2(min) Unretained 0.90 - Benzene 10.90 0.400 Benzo[e]pyrene 13.30 0.400 Pyrene 16.70 0.450 Coronene 26.10 0.500 3 3. Two species, A and B, are separated on a 2.00 m long column which has 5.000 x 10 plates when the flow rate is 15.0 mL/min. A species that is non-absorbing and known not to interact with the stationary phase, elutes in 30.0 s. Compound A elutes from the column in 5.00 min and Compound B elutes in 12.00 min. Calculate the relative retention. 4. No calculation 5. No calculation 6. Calculate the volumes (in mL) of mobile phase and stationary phase in the column described in Question 1. 7. No calculation 8. Two species, A and B, are separated on a 2.00 m long column which has 5.000 x 10 3 plates when the flow rate is 15.0 mL/min. A species that is non-absorbing and known not to interact with the stationary phase, elutes in 30.0 s. Compound A elutes from the column in 5.00 min and Compound B elutes in 12.00 min. Calculate the peak widths (in seconds) for Compounds A and B, respectively. 9. Using the data in provided in the table in Question 2, calculate the relative retention for benzo[e]pyrene and pyrene. 10. Using the data provided in table found in Question 2, calculate the resolution for the two components, benzene and benzo[e]pyrene 11. No calculation 12. No calculation 13. No calculation 14. An organic base (B) has a pKa of 6.950 and a partition coefficient, between water and ether, of 3.0. The organic base is extracted from 225 mL of a 0.175 M aqueous solution of B, that has been adjusted to a pH of 8.00, with 75.5 mL of ether. Only one extraction is performed. Calculate the concentration of the organic base (B) in the water phase after the extraction. 15. How many 50.0 mL extractions with an organic solvent will it take to remove 95.0 % of a compound (lets call it Compound X) that is in 20.0 mL of water? The partition coefficient of compound X between the aqueous solution and this organic solvent is 0.30.
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