Separations KEY (v.1)

Separations KEY (v.1) - Third Exam Chem 241 April 12, 2010...

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1 E = electric field strength = volts/cm Third Exam April 12, 2010 Name: _____KEY-1 _________________ Chem 241 Professor Jorgenson (please print full name) Honor Code Pledge: _____________________________ ( s i g n a t u r e ) R S 2t 2 t 1 W 1 W 2 V R V M KV S H L N A B u Cu K 2 K 1 k' 2 k' 1 t 2 t m t 1 t m m m r M S M M S S t t t V V K V C V C k' D KH  K a H   D KK a K a H   t r t m 1 k'  L u 1 K V S V M Q n V 1 V 1 KV 2 n K C organic C aqueous K C stationary C mobile 1 4 R S N 2 2 S needed 1 1 16R N t' r t r t m I 100 n N n Log t' X Log t' n Log t' N Log t' n velocity apparent E apparent = ep eo 2 H 2 r 2 B 2 r 2 t 2 r W t 5.55 W t 16 t N 1 2 t t
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2 Name: ____________ ______________________ (please print full name) Answer Page: Using BLOCK CAPITAL LETTERS write the letter of your answer to each problem in the space provided below 1. _____ 2. _____ 3. _____ 4. _____ 5. _____ 6. _____ 7. _____ 8. _____ 9. _____ 10. _____ 11. _____ 12. _____ 13. _____ 14. _____ 15. _____ 16. _____ 17. _____ 18. _____ 19. _____ 20. _____ The following three problems make use of the information in the graph below pH 01 4 2 4 6 8 10 12 A B C D i s t r b u o n R a 0 5 10 15 20 The chart above shows the behavior of a three substances distributing between diethyl ether and an aqueous phase. Using this chart, answer the following questions: 1. What is the pKa of substance C? A) 17 B) 18 C) 8 D) 9 E) 3 F) 13 G) 4 H) 10 2. What is the partition coefficient of substance B? A) 17 B) 18.5 C) 8 D) 9 E) 0.5 F) 13 G) 4 H) 10
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3 pH 12 aqueous solution containing A ,BandC extract with ether first aqeuous fraction ether fraction extract with pH 6 aqueous final ether fraction second aqueous fraction 3. All three substances, A, B and C, are mixed together in an aqueous solution and separated following the flow chart shown above. Which substance is found in each fraction? A) final ether fraction: A, first aqueous fraction: B, second aqueous fraction: C B) final ether fraction: A, first aqueous fraction: C, second aqueous fraction: B C) final ether fraction: B, first aqueous fraction: A, second aqueous fraction: C D) final ether fraction: B, first aqueous fraction: C, second aqueous fraction: A E) final ether fraction: C, first aqueous fraction: A, second aqueous fraction: B F) final ether fraction: C, first aqueous fraction: B, second aqueous fraction: A 4. The weak base pyridine (P) is dissolved in 100 mL of aqueous solution buffered at pH 5.0. The K a of HP + is 6.3 x 10 -6 . The partition coefficient, K, for this compound between water and ether is defined: K = [Pyridine] ether /[Pyridine] water = 20.0 With the aqueous phase buffered at pH 5.0, how many times would the 100 mL of the aqueous solution have to be extracted with 50 mL of ether to remove at least 99% of the P and HP + from the aqueous phase?
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Separations KEY (v.1) - Third Exam Chem 241 April 12, 2010...

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