322a lab quiz 1 spring 04 key

322a lab quiz 1 - CHEMISTRY 322aL ‘ pra(L‘C fluf-krFIRST LAB QUIz—(WW NAME 1(11 2(9’ Lab time 3(14 T.A 4(12 5(10 6(6 TOTAL(62 This test

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Unformatted text preview: CHEMISTRY 322aL #/ ‘ pra ({(L‘C fluf-krFIRST LAB QUIz— (WW NAME . 1.(11)___ 2. (9’) Lab time 3.(14) T.A. 4.(12) 5.(10) 6. (6) TOTAL (62) This test comprises this page and six numbered pages. If a question says to answer in fewer than a certain number of words, DO SO. Deduction for wordiness. pair—U '1' (:W“/L quf 1. (2) A 14/20 female (outer) standard taper joint like that on your 25 mL RB flask) is made of glass 1.0 mm thick. Calculate its inside diameter (ID) at its narrow end. (er I Tax‘wf' ()3 J“ a .20 MM MVVMM (’1‘! Mat) :7 a 1’ \[LWLWZ (2) For a 2.0% (by mass) aqueous soln of glucose (Mngucose = 180, 6 W1! mwwater = 18), calculate the mole % glucose using the dilute solution approximation. L14 h4c : "'—%E3_- hole 0/0 JIMC': vu—J W“) yr? 2.4... 2- m . . ,3}: :1“ ‘ 78“ IOO'IwH‘Q‘ MW a” 14036“ : 0~LMI££ 3. (3) A pure organic liquid containing C, H, and 0 shows strong C-H 1. only absorption in the infra—red, but no other strong absorption ig‘ Iabove 1550 cm'l. What oxygen—containing groups of atoms are 3% excluded by this result? Use <5 words; drawings OK. '1 ‘W \.. - .— Jéhpwr‘th—wl‘u (0'0 "k OH 4. (2) Complete the following sentence, referring to the VfiA: The boiling point (in general) of A is 30:50*f37jr£&¢j m fiMflVW 42¢ wéttk Jljuaé m {fifQYMbZ/WW. 5 (2) Below is the distillation curve for a 100 g of a solution of A (lower boiling) and B. There is no azeotrope in this system. z 51% ==II III-IIIQI====== I III-Ill- lllllll IIII IIIIIIIIIIIIIIIIII IIIIIIIIll-E=:::h- IIIIII IIIIIIIII lllllllll IIIIII II Ill-II IIIIIIIII Below, circle one of the items separated by / in each set. From the curve, B's bp is lower [figfififii than =84°, and the original mixture was about 55 / 60 / fiE’/ 70 / 75 / 90 % A. 7.7 4'27 6. (2) Water and Formic Acid have ~nbp's; both have strong H-bonding in the liquid. Yetzflivap and.4£§ap for W are ~1.5 times those for PA. State what difference(s) in their yapgra aCcount(s) for this. Use <10 words. ’ MAM 0L Mrwtg [ofi W'WOC) vapor,“ Ffi Add ALAWCO; Woo) vdfar 7. (3) An aqueous solution containing 20.0 mL isopropyl alcohol (IPA, d = 0.78) is "salted out". The upper layer weighs 13.2 g and has a volume of 15.0 mL. Using the table below, determine the layer's composition and calculate what fraction of the origi- nal 20 mL IPA is in the upper layer. . -_ _._ n&.7X%L 8...... .. % 02% 13M “0 “ L . it"t 0.9900 6.5 . :(5‘. 66 _ 0.9800 (3 1 C9 7/ (wé at 0.9600 . ~ . 0.9400 30.1 garb :3 (’u' ‘4 09200 45.0 0 “ 0.9000 53.5 0.8800 61.9 (AL km. 5‘ (67/40 0.8600 70.3 0.8400 78.68 0.8200 86.88 # ML hm 0.8000 94.80 0.7900 98.60 0.7863 100.00 8. (2) Compound C, MW = 108, is steam distilled when Pexternal = 760 torr. If P°W(ater) = 660 torr at the mixture's bp, calculate the mass ratio in the distillate; MWwater = 18. W% 9. (2) W(ater) andcxknous cpd D are mixed. Two liquid phases exisa “j at equilibrium—-one is 1.0 mole % D, the other is 5.0 mole % C) (A ‘149 W. Assuming that in each phase, Raoult's Law applies to the £2017? majority component and Henry's Law to the minority one, give Ptotal for the W—rich phase, in terms of P°W and P°D. Lo)!ng Ptot, W—rich phase = 0. 1 7+ 4 early rev-«W i'fi‘f" 3 ' NW2”C « 10.(4)(a)(2) A Dggglg Agent forms only a dih - the DA/DA-ZW has rel humidity = 16%. If one adds a —fold D excess to a soln of 3.0 wt % W in an Org Solvent, calculate the final W conc. 3.0 afloat) >0 0.16 '2 (0.9% 6.13% 6t} (b)(2) For the solution above treated with a DA of capacity 0.20 g W per 9 DA, calculate how much DA is needed to dry 500 g W—satd O fQL 2E. .Assume all the W is removed. a»? Manx 05W 500‘? )C 0.03 ‘If LJ ZWUJI‘M’ “fiqu “WI/{‘5 ‘ 753/4 03L am/ 11. (6) For cpd F, KVB/VA, (i.e., z) = 6. Calculate the fraction of F unextracted [FUE = 1/(1 + (z/n))n] for (a) use of B all at once, and (b) use of B so FUE is minimized. Take e3 = 20. (b) (2) Id" 00 l (a) (2) “2‘ . I f: 4 row: 7;.— W m w an) I I: J; (<9. H3) (c)(2) For 2 > 6, the superiority of (b) to (a) (circle one choice)—- gets even better. stays the same. decreases. 12. (2) On mixing liquids, volume, unlike mass, is not necessarily 0“: {v conserved. Considering this, tell what the phrase "70% iso- volume“ means. Use <15 words. w I”- propyl alcohol by “"22 “5" “704/. NW A; v.1 ” mm mm w W“ ‘ ‘ 5/) NF 3d \\ ‘ V I % [00 v NJ 47/10“,ng '70 vols 4 I“ 0:] Sn!“ . 10 (2) J has mp = 100°, and L has mp = 140°. The most probable mp for a mixture of 90% J and 10% L is (circle one answer)—- 72° 104° 120° 136° 144° in Ill/4* 14. (3) A certain sample X, of mp = 75—80°, largely cpd M or largely cpd N (but could contain neither). A mixture melting point with pure M of mp = 82—83° is 68—69°; a mmp with pure N of mp = 90—91° is 77—81°. Tell what these data say about the likely composition of x; give reasoning. X a3 fiwjf/y (0/)! IV {Chet aMw‘a H h x [cu/4g X5 mfl is suspected to be either /’ (OJ: MMfl XHI 7 “to X/ 15. (6) A solid sample comprises 9.0 g P and 4.0 g Q, whose solubilib ties in a solvent S are independent. The solubility of each in hot S is 5.0 g per 100 g S. In cold S, P‘s solubility is 1.0 g per 100 g S; Q is four times as soluble. (a)(2) Calculate the minimum amount of S needed to keep all the Q in solution after cooling. Show calculation. \ SCMLQ wlr/ @[ué 462 o 258% 5. M. M. .. WM £27m}; thJJfMa/vzbafl' 5”“ ?8U%gp/00JJ .: I / X0 (c)(2) If the initial dissolution in hot S gives a colorless solution with some brown goo sticking to the flask walls, tell what one I 8011 onex. se< WI . ~— (’fl h 1dd t U 10 ods bu” Q‘H’a. (00% (gr d/‘chflaé' (AIL? MW 16. (3) Glucose (dextrose, grape sugar) has mp ~ 148°. Addition of 1 fr g water to 6 g glucose depresses its mp to 95°. Restate these data in solubility terms; refer to a temperature, the nature .aacA- of the solution (dilute, conc, saturated), and to solution 1 WM . Composition in ma fragt'égn glucose. fol” ”"_’fl__,__,________. A7240” 17.(10) Recall the preparation of n-BuI: acetone , ' n-BuI + NaBr MW :1 184 1.61 (a)(4) Suppose one starts with 4.11 g n-BuBr and 5.0 g NaI. Calcu- late what volume (in mL) of n—Bul corresponds to a 70% yield. You may leave your answer factored. Mm Mm- 2% WM (37w7/w/ MM (b)(6) While t—Bu-Br is inert to NaI in acetone soln, it does react in a solution of 5 mole % NaI in ethanol, giving NaBr in high yield. But the main organic product is not L—Bu—I even with NaI in excess over t-Bu-Br. (1) Tell why t—Bu-Br reacts in ethanol but not in acetone, (2) draw the principal neutral organic product, and (3) explain why your answer to (2) rather than the iodide forms preferentially. lréc/[o (‘1 (WW «(lam Wafim» Cam? % 3g) + ;. 54), mm. ' M i=6 18. (6) Note the data below: N R a i 139 ihfiéll (1) n-Bu-Br ----> n—Bu+ + Br' + 178 (2) NaI ---—> Na+ + I' + 164 ('1 (3) Q—Bu+ + I' ----> n-Bu—I — 171 r-a (4) Na+ + Br" ---—> NaBr - 174.5. Sum: n-Bu-Br + NaI -—--> g-Bu—I + NaBr - 3.5 (5) NaCl ——-—> Na+ + c1" + 183¢—' (6) n-Bu—Cl -—--> n-Bu+ + C1’ + 185'—‘ (a) (3) Calculate Aaoverall for the reaction:. n-Bu-Cl + NaI ---->g Q—Bu-I + NaCl, showing your calculation. _f’,,flq Watc/ __,-y. 3364’”* Cl“ +135 “:3: ’7» Uu@ 1L£@ 'F /é‘7L Avg“? Fr@ .1"- fi-é’q-J: ‘(7/ Ala“ +0" A ’WC/ ‘1“ .50 flWAML? (OHM {Um V?” at :. Aggwaa'aw” (b)(3) Explain why even though the reaction path does not actually include the numbered reactions above used to calculate 11G for the overall reaction, the calculation is still valid (assuming ' N . . . the effect of the solvent acetone on (XG 1S negligible). Use fewer than 25 words. 5\ 6 ~ {7LM MS” ...
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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 - CHEMISTRY 322aL ‘ pra(L‘C fluf-krFIRST LAB QUIz—(WW NAME 1(11 2(9’ Lab time 3(14 T.A 4(12 5(10 6(6 TOTAL(62 This test

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