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practicelabquiz

practicelabquiz - CHEMISTRY 322aL M W 44 566000 mCfi 22...

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Unformatted text preview: CHEMISTRY 322aL M W 44/ 566000 mCfi 22, fM’IL‘DQJ P FIRST LAB QUIzteJ” — fay/1M L00)? BY Big: NAME Lab time Tim 65% W /-§,//./‘L 4' gr 53.5" 71w 6]“, gm ?l0)[3"/g 5. This test comprises this page and five numbered pages. If a question says to answer in fewer than a certain number of words, DO SO-—deduction for wordiness. Show work for calculations. TAB will have quizzes at office hours and make-up labs, week 0 Tuesday mo ' 9 lab convene or grading questions, please see yo first. -1- enter 1. (2) A 19/35 female (inn-r) standard taper joint has a 1.0 mm thick wall. Calculate its inside diameter (ID) at its narrow end. 2. (2) Metric O—ring size is specified as "IDxOD", both in mm. Circle the size which will just fit without stretching in a circular groove of ID a 8.0 mm and width - 1.5 mm. 8.0x9.5 6.5x9.5 8.0x11.0 8.0x9.5 9.5x11.0 3. (3) An organic liquid contains only C, H, and 0. Its IR spectrum shows only C-H stretching above 1550 cm‘l. Name or describe what functional group is indicated. Explain in <15 words. 4. (2) An aq soln containing 25.0 g isopropyl alcohol (IPA, density a 0.78 g/mL) is "salted out". The 20.0 mL Upper Layer weighs 17.2 g. Using the table below, calculate ONLY what fraction of the UL is IPA. ZERO it give information not on point. 1:!”- zlfllehoLn‘Z, dam) on ammo 1&3 saw as 0mm ”J demo ¢ao man) 515 03a» 6L9 saw we sum 71% saw was 0mm aim 01w» gsw Gian lfllm , ’ I-IlllIl-m-l __ 5 (5) Heavy water (D20), formic ; 3 , “w. , ac1d (FA, HC(O)OH), and n-BuBr . ' ‘ mfg; - _- all have nbp's ~ 101°,- see _ , ——,I,’ drawing to the right. =I' ’ 7I ‘_“-7 ’ __ In the blanks below, write (vi-fij—n , the letter of the VP vs T f “=:' -—-¥*-—__—_- curve corresponding to each: Ill-laid ‘ _ _.___ FA __ n-BuBr __ 1320 __ ‘ — ;_.__ " T._. ._ At pressures above 760 torr, e.g., 780 torr, which liquid has the highest bp? A B C (Circle one letter.) - 2 _ 6. (2) Define normal bailing paint (nbp) by completing the following sentence in <15 words: The nbp of any liquid is 7. (3) Compound C, MW a 162, density = 1.25 g/mL, is steam distilled. Pextemal = 720 torr; P°W(ater) = 640 torr at b _ pmixture' Calculate the volume ratio in the distillate; MWwater = 18. ~ 6 P° W OCT After phase separation, which has the larger partial POCT' (1) immediately after separation? $1 @2 neither; (2) after ~20¥ of each 0 has evaporated? él @2 neither. 9. (3) A Drying Agent forms only a dihydrate; the system DA/DA-2W has relative humidity = 10%. One adds a 3—fold excess of DA to a halt-saturated soln, which contains 2.0 mole % Water. Calcu— late the final W cone, in mole %. [fit 10. (3) The solubility of Water in an Organic Solvent is 0.30 wt %. A DA has capacity 0.20 9 W per 9 DA. Calculate how much DA is needed to dry 3.0 kg W;satd OS. Assume all the W is removed. 11. (2) Ethanol has nbp = 78°; non—toxic. Tell in <10 words why it is not used r extracting aqueous solutions. it is readily available and relatively outinely for -3- 12. (6) For cpd F, KVB/VA, (i.e., z) a 6. Calculate the fraction of F unextracted [FUR = 1/(1 + (z/n))n] for (a) use of B all at once, and (b) division of B into three equal portions. (a)(2) (b)(2) (c)(2) As 2 decreases, the FUE for (h) compared to (a) (circle one)-- decreases, which is better increases, which is worse decreases, which is worse increases, which is better 13. (3) Pure J has mp = 86°; pure K's mp = 92°; a certain sample X melts 78° - 83°. Mixture mp K and X a 73° - 76°~ mmp J and X I [1152 21/ a 82° - 84°. Giving your reasoning in <15 words, tell if the likely major component of X is J, K, or neither. 14. (3) Sucrose (ordinary table sugar) has mp = 175°. When a mixture of 1.0 9 water and 9.0 9 sucrose is carefully warmed from 10°, the last solid sucrose disappears at 23°. Restate these data in solubility terms; refer to a temperature, the nature of the solution (dilute, conc, saturated) and its composition in terms of wt *‘s. ZERO for any reference to mp depression. 15. 16. 17. 472M2/ofixqér 149.14 (4) A solid sample comprises 10.0 g M and 3.0 g N, whose solubili~ ties in a solvent 8 are independent. The solubility of each in Del 8 is 5.0 g per 100 g S. In cold S, M's solubility is 2.0 g per 100 g S; N is twice as soluble. Calculate the amounts of S needed (a) to just dissolve the whole sample hot, AND (b) to just keep all the N dissolved in gold S, after boiling down filtrates to recover more M. (2) A solid sample heated with solvent gives a colorless solution with brown goo stuck to the flask bottom. In < 12 words tell what should be done next in the recrystallization procedure. (125 4 on Recall the preparation of n-Bul: this page) acetone n-BuBr + NaI ___________9_. n—BuI + NaBr MW = 137 FW = 150 MW = 184 d = 1.27 d, = 1.61 (a)(4) Suppose one starts with 60.0 mmol n-BuBr and 10.0 g NaI. Calculate how many mL n-Bu-I corresponds to a 70% yield. l7. (contd) w flag}? fir L'Q'L‘ . Reactinn (b) (a) A; lhcal). (1) n-Bu-Br -———> n-Bu+ + Br‘ + 178 (2) NaI ---—> Na" + I‘ + 164 (3) n—Bu+ + I’ ———-> n-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‘ + 133 (6) n-Bu-Cl ----> n-su+ + Cl‘ + 185 Sum(C1): n-Bu‘CI + NaI ----> n-Bu—I + NaCl - 5.0) Keq~2000 (i) (2) Given that the rate—determining step is (X = C1 or Br): I' + n—Bu—x ------ > n—Bu-I + X" calculate '23(a§"),aA‘€;’x_Cl ‘Aé’fi-Brl assuming each term equals the dififimnqg between the BDE of n—Bu-X and n-Bu-I. (Reverse the signs of the data above as needed.) p) (ii) (2) The rate ratio, X=Br:x=C1, is exponential inAuG"), For this rxn, a 1 kcal/mole decrease inAA'é‘fi 1119133535 the ratio by a factor ~4.5. Calculate the rat ratio XaBr to X=Cl. tell whether the difference in rates or in the Keq's is more important. Explain using < 25 words. 18. (4) Both n—Bu—Br and t—Bu-Br react readily with excess NaI in EtOH giving ~100% yields of NaBr. Write the principal neutral organic product for each reaction: ...
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