Organic Lab Test 1 pdf

Organic Lab Test 1 - “Version 1“ Name Lab TA CHEZ 30l FirSl Organic Lab Test June 29 2005 For each of the following questions mark the correct

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Unformatted text preview: “Version 1“ Name: _ Lab TA: CHEZ 30l FirSl Organic Lab Test June 29. 2005 For each of the following questions, mark the correct answer on the answer sheet. Each entree! answer is worth 4 (four) pnint‘t. .1. When may sandals be worn in lab? . only when the TA is not watching . only when the instructor is not watching ill all times a b (J. [{D never 3. A solid compound has a melting point of 150°C and is very soluble in hot_\_t;a;e.r_‘_§old water. hot ethanol. cold ethanol and hot attetone. It is insoluble in hot ethyl ethert‘eold ethyl ether. and cold aeotonc. What solvent system should he used to recrytnallize the solid?“ ' -- :3. ethanol h. ethyl ether L‘. \N ‘ mo 3. A compound has a literature melting point of GOT and a boiling point of 23 KT. What method should be used to purify the compound? recrystallimtion w distillation t‘. reflux 4. The solubility ot‘a solid in ethanol is 2.30 gr‘IOO ml. at the boiling point ofethanol and 0.11 gtlDU ml. at 25"C (in ethanol]. What is the minimum volume of ethanol required to dissolve 0.58 g ofthe solid at the boiling point ol‘elhanol'.‘ __ 9.1%. “'79 u. too mt. 343..) " 30?. " h. 50ml. ‘3 -- C725 _ .. 2- 1 ' mL .4 5. .-\ solid is m'CQ'stallized from an appropriate solvent. If the student started with 2.00 g of solid and obtained LSD g of recrystallized Solid. what is the % recovery? :3. 20 “xi: I" :- 5 _ n; ...‘..—-v—_-" :r ‘ b. hi -) r c. 15 to t .S _ , _ —- A roe : 6. A homogeneous mixture contains two liquids (Compound A and Compound B). The boiling point of _ pure Compound A is known to he l??°C. The boiling point of pure Compound B is known to be l97°C. What process should be used to purify the mixture’.J a. recrystallization A " ll." h; simple distillation ,9 I; c. 2‘ fractional distillation ' cl. sublimation 3.. "i. In which type of distillation are glass helices used? simple distillation ' . Fractiona lstt ation a. ll. Which type of distillation has more theoretical plates? simple distillation .. fractional distillatio a. h C. d 9. A homogeneous mixture contains a 502’50 mixture of Compound A (boiling point WT) and Compound B (boiling point 120°C). A simple distillation apparatus is set up to separate the two compounds. Which compound should be in the higher percentage in the lirst mL of distillate? Which compound should he in the higher percentage in the last mL oi'distillate'? k --a. first — Compound A ' . first P CompoundB c. first h Compound A d. lirst — Compound B last — Compound B last — Compound B last — Compound A last -- Compound A 10. What is a theoretical plate’.J The distance a Buchner funnel is From the aspirator . The diameter of a Buchner funnel A cycle 01‘ condensation and revaporization in a distillation . The percentage of impurity in a solid sample 1 l. A solution in dichloromethane contains a phenol {mp 110T, hp 230“C) and a carbonylic acid (mp 80“(‘- hp 2]0"Cl. W hat should be the sequence of steps used to separate the two compounds via extraction.J Evaporate the solvent to give an impure mixture of the compounds and then distill to separate the two. Extract the solution with aqueous sodium hydroxide solution, separate the layers. and then acidify the aqueous layer. Then evaporate the organic layer to give a solid. Extract the solution with aqueous sodium bicarbonate solution. Separate the layers. and acidifv the aqueous solution. Then evaporate the organic layer to give a solid. . Acidil’}; thc dichlorotnethane solution with aqueous hydrochloric acid. 12. Two immiscible solvents are put into a sepamtory funnel. Which solvent is the top layer'iJ Solvent A — bp 210°C. density 0.76 gimL Solvent B — bp 110°C, density 1.4 giml. ) Solvent A h. Solvent B e. Only one layer is formed .13. What sequence of steps eculd be used to separate a dichlortflthane solution oFa carbonylicqaeid. a phenol and an amine (a basic compound)? 3. Extract the phenol into aqueous sodium bicarbonate solution, separate the layers and acidity the basic layer. Then. extract the carboxylie acid into aqueous sodium hydroxide solution. separate the layers and acidify the basic layer. Then. evaporate the dichloromethane solutiort to give a residue of the amine. __ b. Extract the carboxyiic acid into aqueous sodium hydroxide solution. separate the layers and acidity the '_ > basic layer. Then. extract the phenol into aqueous sodium bicarbonate solution. separate the layers and acidify the basic layer. Then. evaporate the dichloromethane solution to give a residue of the amine. e Extract the amine compound into aqueous hydrochloric acid solution. separate the layers and make the acidic layer basic. Then. extract the carboxylic acid into aqueous sodium bicarbonate solution. separate the layers and acidify the basic layer. Then extract the phenol into aqueous sodium hydroxide solution. separate the layers and acidify the basic layer. [4. What is the purpose of a "drying agent?“ i'-'"'“‘\ la. lto remove water liom an organic solvent ii. to evaporate a liquid to dryness e. to cause 2 miscible liquids to form 2 layers d. to give more theoretical plates in a distillation 15. Which of the following compounds should he the least polar? {it/“é GP KIM-uh.» (It; l._ v I I I; O “mi: 6-) E‘l-"jlil— I; 5 .'" 43."; l___ _ I ‘ \ ,/ at. V b. . C. I if). A TLC is eluted on a silica gel plate. Three individual spots are seen on the developed plate. Compound A has an R,— of 0.7. Compound B has an R.-ol'0.3 and Compound C has an Rrol‘Ul. Which compound is more polar? :1. Compound A H _ _ ? b.~~£orupound B _ I. like. Compound C ' ' t d. they-all have the same polarity. ’a. the more 4 17. The compounds (3 of them) in a mixture are separated using column chromatography (silica gel). Which compound will elule off the column first? in: ."the’more non-polar compound C. an mp0 n ' ctmediate polarity 18. A TLC plate containing a sample is eluted. The solvent moves 10.0 cm and the spot moves 4.0 cm. What is the compound's Rf? 3’ 5' “.2 3-0 if. I -; 1 0 E 9 _: G; 19. Why is the origin on a TLC plate marked in pencil instead of pen'? Because pen in}; is comprised of organic pigments which may separate during the elution. ‘-_ Because pen will destroy the integrity of the adsorbent ' Because pencils are less expensive than pens Because pens come in diiferent colors, some of which may not show up under uv light or iodine. 20. During the resolution of(+)-phenylsuccinic acid from a racemic mixture ofphenylsttceinic acid. {-i-proiine was used to make an insoluble his salt of the (+)-phenylsueeinic acid isomer. What physical property allowed the separation to take place? a. boiling point h. soluhilit) c. melting point d. molar mass 21. Of the following solvents. which is the least polar? / flua '51 “L W a. acetone - - ' ' ' 6+“ ' b. methanol-- " ' M ¢H1 . . WW (3. acetic acid' if 32. What is the process called when a solution is heated at the boiling point of the solvent for an extendedperiodgftinte? " ' “' " _ '_"_'_'H__‘“ .51., recrystallization b. reflux c. high temperature distillation d low temperature distillation Xena /-~W Pp? ..‘ 3‘" F+¢Lm 23 — 25. Idenlil’y the lab equipment item the following possibilities: Buchner funnel Separately funnel Liquid funnel Thomas Adapter Powder funnel a. b. c. d. e. t J U: ...
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This test prep was uploaded on 04/18/2008 for the course CHEZ 301 taught by Professor Moses during the Fall '07 term at VCU.

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Organic Lab Test 1 - “Version 1“ Name Lab TA CHEZ 30l FirSl Organic Lab Test June 29 2005 For each of the following questions mark the correct

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