322a lab quiz 1 spring 05 key

322a lab quiz 1 spring 05 key - ' CHEMISTRY 322aL April 4,...

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Unformatted text preview: ' CHEMISTRY 322aL April 4, 2005 SPRING 2005 FIRST LAB QUIZ NAME / ; 1.(12) 2 (12) Lab time 3.(12) T.A. 4.(10) 5. (9) This test comprises this page and five numbered pages. TOTAL (55) If a question says to answer in fewer than a certain number of words, DO SO. Deduction for wordiness. TAs will have quizzes at office hours and make—up labs, week of Apr 4. Monday evening lab convenes at 7:00, Tuesday morning lab convenes at 9:00. For grading questions, please see your TA first. [ V‘V‘ / i « /;L - 1 - _/ w 1. (2) A 24/40 male (inner) standard taper joint (like that e’ '~=‘ ’ {9 lower end of your reflux condenser) is made of glass thick. Calculate its out::?e diameter (OD) at its narr w end. If—QT—O 36>be 060m fie “4M \ é. if J; .{Zfif‘ m 40—: $41.44!“ MM % M11472 2 (2) An 8—mm ID O—ring just fits in a groove of OD = 11 mm. late the O—ring's thickness. fl-z/uk MM. a-m‘w w‘ gem. 3““ 2/.(Mf_ W (Z? 4,40 7/ 470/“ OZ flag/Aw Mm X16621?qu 3. (2) A bulk grade liquid sample shows moderate absorption at 3400 cm'l. After treatment with anhydrous CaClz, the 3400 cm‘1 absorption is very weak. Explain in < 12 words. (.62. a {W In W J ‘ w cm» or . (41M U ’ 3+ MOI/Mfg 4. (3) An aq soln made up from 15.0 mL isopropyl alcohol (IPA, densi— ty = 0.78 g/mL) is "salted out". The upper layer weighs 12.0 o g; its density corresponds to 75 wt 6 IPA. Calculate what fraction of the original 15.0 mL IPA is in the upper layer. MW 0441”! f/fl‘: {s’nL $0.7X 7/mL :: MIC}. l1; “L v3 7fl4@€] ‘ “L. HAL-r? 100 ‘M M/J y : {7704) (0.77) m 5. (3) Define normal boiling point (nbp) by completing the following AL sentence in <15 words: The nbp of any liquid.is .. {‘er m “Af ,3 m ¢u¢d “fl2,ufifl£J‘v w” (M‘ A /( («V633 V‘ylor “f N C 7&7 {om Wm M A w Sgt/7M «TM/km) [0&7 —2— 6. (4) Heavy water (D20), formic acid (FA, HC(O)OH), and n—BuBr all have nbp's ~ 101°; see drawing to the right. 1% In the blanks below, write r6, the letter of the VP vs T / curve corresponding to each: 2 D20 C FA Q—BuBr 8 At pressures belo '- torr, e.g., 740 torr, which liquid has the lowest bp? a B C (Circle one letter.) Compound C, MW = 162, is steam distilled when Pexternal = 720 torr. If P°W(ater) = 640 torr at the mixture's bp, calculate the mass ratio, in the distillate; mwwater = 18. flaw/~00!) (7 W60 64"? gW/gC=/‘f :/ c. 640 1/ “(we g/mlec/ 1w (ans/f”) 75C 8. (2) W(ater) and odorous cpd D are mixed. Two liquid phases exist 3 {1‘- A at equilibrium-—one is 2.0 mole % D, the other is 6.0 mole % (9,... W}. Assuming that in each phase, Raoult's Law applies to the M db majority component and Henry's Law to the minority one, give 0 Ptotal for the D—rich phase in terms of P°W and P° 4 ' D- O 0 0846141” Ptot, D-rich phase = ’3” Mum . 9. (2) A D ing Agent forms only a trihydrate; the system DA/DA-3W has relative humidity = 15%. One adds a slight DA excess to a half—saturated soln which contains 2.0 mole 96 Water. Calcu- ‘km late the final W conc, in m'ole %. L7,); 54% y [K ()1 c‘.) 10. (2) A Water—saturated Organic Solvent is 0.50 wt % W. For a DA with capacity 0.30 9 W per 9 DA, calculate how much DA is W needed to dry 3 kg W—satd OS. Assume a; the W is removed. MON} 400 W 300051,:qu ’0 MN? L cm a (00 ad.‘ 0 73 N ‘ mm#{ a If “270,4 W 2:32.“. =M=W M i’I/fl ~3- 11. (3) An unrinsed Single Laundry Load (SL) retains 5.0 % soln (FSRSL — 0.05) on spin drying, with detergent residue per mass = C . One rinse-and—spin thus leaves C = 0.05 C . 0,SL , 1,SL 0 SL For a Quadruple Load, calculate CQL in terms of C0 SL for three ras. Take cO QL = 4 c0 SL and FSRQL = 4 FSR'SL. Tell what your calculation means regarding the final detergent concentrations for (SL, 1 ras) compared to (QL, 3 ras). Yo'vt 6M WM .3 3 CQLLqu = (0(QL(p5(&L3 :; ‘t‘GJLZLILFVEL—J : 4G2.“ (0.2.)3 =1 460,31 (0.00%) 2 '523T2;E£;:23325;2:i) (:k[_\ 3 waa [2431 45551 éflltfzefi;_ Mc‘MM W W SL,.ZW 12. (2) Ordinary alcohol, ethanol, is cheap and readily available, volatile, and relatively non-toxic. Tell in <10 words why it is not used routinely for extracting a eous solut'ons./ Mthé/e wrfl a) at “gaze/"7) W [4YJL/ 13. (2) G has mp = 100°, and H has mp = 140°. The most probable mp for a mixture of 95% G and 5% H is (circle one answer)—— 80° 95° 105° 120° 135° 145° 14. (2) A solid sample J has mp = 69 — 72°. A purification process gives good recovery of material of mp = 71 — 73°. Did the process likely purify J? Explain your answer in < 10 words. 1% YM) W/fwlj F9%,{M¢/A® 04A M 15. (3) Sucrose (ordinary table sugar) has mp = 175°. Addition of 1 g water to 3 9 sucrose depresses its mp to 65°. Restate these data in solubility terms; refer to a temperature, the nature of the s51fif155—UEITGEE, conc, saturated), and to solution /6¢([1 composition in terms of wt fraction sucrose. may 45 w, a «fizz/2146M) -4- i: 16. (4) A solid sample comprises 9.0 g M and 3.0 g N, whose solubili- ties in a solvent S are independent. The solubility of each in hot S is 6.0 g per 100 g S. In cold S, M's solubility is 1.0 g per 100 g S; N is four times as soluble. (a) Calculate the amount of S needed (a) to just dissolve the whole sample hot, AND (b) to just keep all the N dissolved in £1” ; fl/ffig [7(513 17. (2) A solid sample on treatment with hot recrystallizing solvent gives a colorless solution with suspended gray powder. What should one do next? Answer s e ificall in < 6 words. w meiy wth 18. (8, 4 on Recall the preparation of n—BuI: this page) acetone Q—BuBr + NaI —————————a—- n-BuI + NaBr MW: MW FW =:?3 = 184 . 7L Q = 1.61 (a)(4) Suppose one starts with 6.85 g n—BuB and 9.0 g NaI. Calcu— late the theoretical yield of n-Bu—I in mL. 1, I, _ g - 6.35 / (llfls; { A6“! k —/ :0.0£0"‘-* 7 '3 JMc :an/MA/C) W \(l‘6[6[ ¢r firgqr : 57 aura/h/ X «A: VIMN/ an»6%; :- amm{wx% 18. (contd) - 5 - g: (7” AG (b)(4) Reaction (kcal) (1) n-Bu-Br -—-—> Q—Bu+ + Br' + 178 (2) NaI —-—-> Na+ + I' + 164 (3) n—Bu+ + I' —-—-> Q—Bu-I — 171 (4) Na+ + Br’ ——--> NaBr - 174.5 Sum(Br): n—Bu-Br + NaI ——--> n-Bu-I + NaBr - 3.5 Keq~200 (5) NaCl -—--> Na+ + Cl‘ + 183 (6) n-Bu-Cl ——--> Q-Bu+ + C1" + 185 Sum(Cl): n—Bu-Cl + NaI ————> n—Bu—I + NaCl - 5.0 Keq~2000 Tell how the solvent acetone facilitates the reaction as done. State specifically whether its effect is mainly on the egui; liprium or on the rate. Then using < 20 words, explain how the solvent affects whichever aspect you chose. 0/ a (Ljflqut d at lit/é [AZ-auuql/ {924/ (ff/e ‘ {gag mm 7‘9 ( Mad/{m LAG/(ma). (Z? vim? A1413, Amt/7 M414] CLCA Ara/W “(LE ( w? 7/ “mi/i kw?) fQfiWztflw’gr 19. (5) Both n- and t-Bu—Br react rapidly with NaI in ethanol, each giving NaBr in near 100% yield. Explain in mechanistic terms: (a) why t—Bu-Br does not react in acetone but does react in EtOH, and (b) what the main substitution product t—BuBr gives with ethanolic NaI-—it is not t—BuI——and why. A z 577% bigotflgk m (W(}€. 3 f/flté 5647/5744 “(4‘ flflé‘tgfllffl 6'65] 1%" MgolJZZ/mg‘f AZg/i'f ( 7‘ ‘ 7514) ié’g‘ré i—afi’ ‘ ’ fizr Lt7’L‘4 CL4fiAC é'é' (f. é;1?§964E) ...
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This note was uploaded on 10/06/2009 for the course CHEM 322A taught by Professor Singer during the Spring '08 term at USC.

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322a lab quiz 1 spring 05 key - ' CHEMISTRY 322aL April 4,...

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