Test 1 - in “Version 1“ Name: Lab TA: Ermi CHEZ 301...

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Unformatted text preview: in “Version 1“ Name: Lab TA: Ermi CHEZ 301 First Organic Lab Test i October 5, 2605 For each of the following questions, mark the correct answer on the answer sheet. Each correct answer is worth 4 (four) points. 3/ C? a. b. 6 All? /1. .J‘ A sample of a solid compound is found to be impure. What method should be used to purify the solid? recrystallization simple distillation fractional distillation vacuum filtration An organic solid (final product) is suspended in an aqueous solution. How should the solid be collected? simple distillation fractional distillation vacuum filtration gravity filtration What is the purpose of using charcoal during a recrystallization? to dry the solution to remove colored impurities to act as boiling chips to lower the boiling point of‘the solvent A solid is soluble in cold acetone, hot acetone and hot pet ether. The solid is insoluble in cold pct elhcr. cold water. hot water. cold methanol and hot methanol. What solvent should be used to recr) stallize the solid'? Sol-d Solvb‘fi‘? mtat‘aq twe. I hh‘im-‘i. N” 1"" at” acetone “We”, inf-Tth pet ether \sattel' tnetltnnol SoirA meat—eta"; mm Pu (-t-Lv" U 500 g:- ol'a solid is recrystallized from an appropriate solvent. 0.300 g ofpuriiied solid is obtained. What is the “to recovery" 3ill'lu 3'05? min A X lb“ = Kat-ale - U tSUO’b 4ll"-u . (1?“ll J. A sample is composed of 2 neutral liquid compounds. One compound has a boiling point of 80°C and the other has a boiling point of 95°C. How should the liquids be separated“? a recrystallization b simple distillation c. extraction using acid-base chemistry @ fractional distillation 7. What is the boiling point of a compound? a. the temperature at which it goes from a solid to a liquid ® the temperature at which its vapor pressure is equal to the external applied pressure c the temperature at which it goes directly from a solid to a gas d none ofthe above 8. What is a "theoretical plate?“ Q) the difference between the boiling points of one compound and another compound 13. one vaporizatiorflcondensation cycle c. the height ofa fractionating column d. the glass helices used in a fractionating column 9. Given the following graph. what is the % composition ofthe distillate that is collected at lOOUC'? percent cyclohexane 100 ED 60 40 20 O 120%,— 115'» 110;— 105'? 100‘- 95* boiling point {'C] 0 2D ‘0 50 BO 1 D0 _ I I percent toluene u Rtl'fit t.'_\elul1c\une. 30% toluene l1 30% excitihcxune. 309:0 loluunt till” it e} clohcxune. 30% toluene L- ) Ill" u L‘_\ L‘lt'tl‘ItJXEiHC. 80% luluunt‘ ng-' Given the following graph, which curve is more indicative of a fractional distillation? m5 I gal _ __ —— t a E l ,5 __ 1 J. ! ’5‘ '— 0 5 H! 15 Ill K mlatllllnll ta.) Curve A b. Curve B (2. Neither d. Both 1 l. The process of moving the desired solute from one solvent to another in which it is more soluble is caUed a. washing b. centrifugation e. distillation (El) extraction 12. When drying 50 ml. of wet organic solvent, how much drying agent should be used? a. ll} g b. 5 0 g c. Si} g QT) enough to remove all the water 13. What does it mean to “dry an organic Solvent?" to evaporate it to dryness to remove residual water from the solvent to remove impurities using charcoal to add enough drying agent to absorb all of the solvent :_r:@m l4. An organic solvent contains a waterdnsoluble carhoxylic acid. it is extracted with aqueous sodium ludroside. The aqueous layer is ac1ditied with hydrochloric acid. What should happen? The sodium salt ol'the carhoxvlie acid should precipitate from the aqueous solution. The earboxylie acid should precipitate from the aqueous solution. No precipitate should form since the carboxylic acid is water-insoluble. No precipitate should form since the carboxylic acid is Still in the organic layer. “(3% l5. An organic solvent contains a water—insoluble phenol (weak acid). It is shaken with aqueous sodium bicarbonate. The aqueous layer is acidified with hydrochloric acid. What should happen? A. a. The sodium salt of the phenol should precipitate from the aqueous solution. h. The phenol should precipitate from the aqueous solution. r c. No precipitate should form since the phenol is water-insoluble. @ No precipitate should form since the phenol is still in the organic layer. 16. An organic solvent contains a water-insoluble neutral compound and a water-insoluble carboxylic acid. The organic layer is extracted with aqueous sodium bicarbonate solution and the resulting aqueous layer is acidified with hydrochloric acid. A solid is formed. What is the solid? Also. what remains in the organic layer? a. The solid is the sodium salt ofthe carboxylic acid and the organic layer contains only the unreacted carbonylic acid. CS) The solid is the carboxylic acid and the organic layer contains the neutral compound. The solid is the neutral compound and the organic layer contains the carboxylic acid. r d. The solid is the neutral compound and the organic layer contains the sodium salt of the carboxylic acid. 17. Give the missing structures: CH3 NaOH HCI ch OH ———-— CH3 CH3 , \ CH3 3 CH3 _ CH 1 CH. . \5 “H ,1 \a Hzc ~. 0. HC *‘r—o-Na+ CHa ‘- ' :. Na (EH _ h. Ll. l9. ee¢® page timers—r m 9 An organic solvent contains a neutral compound and p-t-butylphenol. The solution is eXIracted with aqueous sodium hydroxide solution. The aqueous extract is evaporated to dryness to give a residue. What is the residue? the neutral compound the p-t-butylphenol the sodium salt of the p-t-butylphenol the sodium salt of the neutral compound What gas is generated when HCl is added to NaHC03? C03 C03 03 H2 When must safety glasses be worn in lab? at all times only when an explosion is possible only when strong acids are being used only when strong bases are being used When may sandals be worn in lab? at all time never only it" safety glasses are worn only if u orking alone ...
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This test prep was uploaded on 04/18/2008 for the course CHEZ 301 taught by Professor Moses during the Spring '07 term at VCU.

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Test 1 - in “Version 1“ Name: Lab TA: Ermi CHEZ 301...

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