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**Unformatted text preview: **CHEMISTRY 322/5aL #1 W Lab time This test comprises this page and seven numbered pages . If a question says to answer in
fewer than a certain number of words,
no SO——deduction for wordiness. 135 will have quizzes at (make-up) labs and office hours. Labs Nov Q (3' Nov Mnre make-up only; TAs will stay one-half hour if no one is doing a lab. Morning labs convene at quD. GC make-up will be only Mon Nov l}, 6:00 p.m. For grading questions on this test,
SEE YOUR TA FIRST. 1. j—
*0 2. 3. 1 I. y“. W KYVC l 5. dgg :, M! §§§§§§§§§§§§i 7+”
4. No
{Va/K29 <2)
14 (2) (4) wall. Faucet washer size is defined why ID and OD alone suffice to specify its size. n‘rcctlm. trots-cec- ﬁﬂ‘ZKWT9E5-0)[email protected] ﬂ 4-Methyl—2-pentanol is made from 4-methyl-2-pentanone. 1 loam. 4w Owl? ﬂai=/3 A 24/40 female (outer) standard taper joint has a 1.5 mm thick mrvw 90 = 5% Calculate its narrow end outside diameter (OD) /O,-=p fﬂ M (.10 + 10.47)“... , D, and thickness.
Referring to the definition of an O-ring, explain in <12 words {f
9 One wants see if the product has 510% unreacted starting material. (a)(2) Near what frequency (cm'l) in the IR should one look to see if
there is considerable unreacted xenon: (circle one number)? 3800 3400 3000 2800 2200 2000 1500 (b)(2) Does the product sample need to be nearly water-free for this M , t4 ("4" (2) (3) IR test to be useful? 2+0? w!
‘ (v: Q.
0:1: 5 U0 . “em. Explain your answer in <15 words. NO. wdg 05m mf’ «MW
(700 cm". A flask flushed with water is thoroughly drained. Tell wheth- er any water film will evaporate faster with the flask neck up, or neck down; explain in <12 words.
vapor normal; effective Mwair Huang, W Va! or (MW 61. (\f, Water has hp s 100°,
= 30, bp ~ -200°. =48) ‘/ {VVIL/ An aq soln containing 27.0 g isopropyl alcohol (IPA, d - 0.79) 383833335885- agggéggeoocno-n¢o is
30
in Lhasa-:95
oa "salted out". .1 g.
the UL. “Log/Wth = 3 (Dii::/, ﬁdnL \ The resulting 35.0-mL Upper Layer weighs
Calculate the ONLY the fraction of the original IPA
NO CREDIT for doing any OTHER problem. ﬂ?»— 0.K6 %L 39/0 a £74,“,
0 N ‘-
3 2 1+16)J I‘M :3: ML
ALL/é : 0. —g;- 160 6. (3)
Note the supposed normal
pressure liq—vapor phase § 6
diagram for cyclohexane E
(CH)/furfural. It errs 3‘20
by saying there is n9 va- 5
par in equilibrium with E “n solns of XCH>0.25.
Assume the liq curve is
correct. (a) What must
be true about the vapor
curve at its minimum
(marked)? (b) What is this composition called? 0.154 Mohfmdmofovdohun (XCH) @g) Uafm cuVVt MAMA—IL ﬂack H? cqume
0(6) Awap-e Ctr/k aétvaO/WC). A 7. (4) Recall that AVP per degree, dP/dT, = P(A§va /RT). Acetone's nbp (hp—,Go torr) = 56.5°C (329.7 K); take A's'vap =
21.5 cal/(mole-K). A tilde, ~, means per mole. (a)(2) Calculate dP/dT (3 sig figs) at nbp; take R = 1.98 cal/mole-K.
ﬁne! that the units come out as torr/K. q
- 1.? 2 ‘ 329-7K
W ,_ M M8 hm»—
# 15.03 1‘W/K Lurrga’. (b)(2) From the above, one can calculate that the boiling point
elevation (bpe) of a dilute acetone soln of Non-Volatile
Solute (NVS) is 0.304° per 0.0100 XNVS. Suppose such a solu—
tion, believed to be XNVS = 0.0600 based on an eeenmed MW = 150, shows a bpe = 0.608°. Calculate the MW of the NVS,
showing your calculation/reasoning. Apt ; @608" a a @301”) =? SJ“
— 0.0300 s; M“ D) /Ji=/0 8. (3) de A steam distills at a mixture hp at which P°W = 7/8 the
external pressure. (1) Calculate the ratio, molesW/molesA, in the distillate. (2) If the distillate has 10 9A per 9 gw,
i.e., per 0.5 mole W, calculate the molecular wt of A. {u _ 7/3 “kite/0'6” _ 5 ‘ —% —W‘ 7 “W” W; arm,” ‘rm‘ua
a =7 'm W5: mag—m Note the data below. "m-n“ in the left column means "a mix-
ture of CaClz‘m H20 and CaClz'n H20 in equilibrium". CaClz hydrate mixture Relative humidity (rh), %
0-1 1.25
1-2 4.2
2—4 14 6-saturated aq soln 30 (a)(2) The solubility of W in an Organic Solution is 5.0 g/L. One has 100 mL of W-satd OS, which also has 4.0 9 W droplets. On
adding 5 - 6 g CaClz, it forms a solid of average formula
CaC12-5W. Calculate the final mass of W in the 100 mL OS. Mm.{ u w: 100 «L Maﬁa: an) 4;;ng : 0.1‘03 x 24% (b)(2) The OS is separated from the solid. A new low capacity, only
0.015 gw/gDA, but Very Efficient Drying Agent is added.
Calculate how much VEDA is needed to dry the CaClz-treated (7 7L soln above, assuming it removes all the water.
anlt ' V :: é‘wr (A7 '3 0 “03/ EM 7' 3‘
MG!) I‘M ‘74'4 c)(3) Leslie the Lab Loser (L3) decided to save time by using enough
VEDA to remove all the W completely in one step. Calculate gVEDA needed just to remove the W droplets from the original
mixture and tell why L3 lost nearly all his/her OS. 0 NM x 167
a La: 0.00? @ “317/ 04 Aéxﬁﬂémﬂftl nag/gala. Yrt‘u/(a a -4- '—
10. (3) A Single Laundry Load (SL) retains 1 % soln and detergent residue = C0 after one ringg-and—spin (ras). A Multiple Load
of size n-SL retains soln fraction and detergent residue pg; mass, Cu, in proportion. (a) Calculate Cfinal, in terms of Co,
for n = 2 and two ras, and (b) n for Cfinal = Co for ras = 2. a (a) OM raw m OM/ [044 {mm aaﬂﬁﬂ’
WM @(b) K2 : ma‘ﬂlln) 2:? u»:— 10 =5?
n=m(~3.lé) 11. (2) In <10 words, state a criterion for an extracting solvent with respect to hailing point :2: the E 1‘: vaf W .11
Kw (04p qv‘ff “(u/fa 7 12. (3) Pure J has mp = 95°; pure K's mp = 92°; a certain sample X
melts 84° - 88°. Mixture mp J and X = 86° - 89°; mmp K and X (::3%;\ <7“ melts 82° - 87°. Giving your reasoning in <15 words, state
the likely major component of X. ‘ CD%\ Xena «MW? X V‘QMW opp/M. XI; min) K4); / c/y («5 WW) I 13. (3) A solid sample comprises 11.0 g M and 7.0 g N, whose solubili-
ties in a solv«. 65°, are independent. The solubili-
\ "(I In mg. 3, M's
( V solubility is 1.0 g per I! g , .0 g per 100 g S.
N" The entire sample is dissolved in 250 9 hot S and then cooled.
Calculate how much each of M and N precipitate; put a nun;
pg; in eagh plank. NO credit without calculation/explanation. 5' M! M Abodfoé
_g_'S:—QM (“fie/L053 g/WW 1.5}? M /%f’ (A (Jet, —_€~)//.0¢-— 24;} 9N : X-faa M 6 46; W1: [/74 2:00 81/ g a... Malta '“ n7i=9 14. (3) Wicked Witch of the West (WWW) is very Water—soluble; at 20° a
satd aq soln is 80 wt% WWW. Restate this in terms of mu depression, giving kg W one must add to 50 kg WWW to lower her
mp to a certain T. Use <15 words; zero if refer to soln or @o lltY- % /_S*K0 w h
rota wwméemmav lm Mp 7" 30‘? 15. (6) The dihaloalkane shown below reacts with either Hal in acetone
or with Agﬂos in Eton, giving one equivalent of inorganic
halide, and an organic product. Write the structure of the
principal gzganig product formed in each case. If and only if reaction occurs at a stereocenter, state whether the center
“W _ _
retains, racemizes, or inverts; otherw1se write "NA". W SFB NaI in acn -—---> 1 NaX+ + org prod
(R)Cl—l—CH2—CH2—CH2-Br
A NO in EtOH ----> 1 A X5 + or rod
CHZCH3 g 3 g g P
Product Stereochem @ 1% W7 0
(a) NaI in C/~-C_C6[V(H‘C”L'r acetone I
EC
\
Product Stereochem @ML Ew-éa/Laxra/L r WWW 95% EtOH / ~ ‘ 0
-\ /“ bf 0 «M7 “in?! Q 'r '6‘ [77436 16. (15 pts, 6 on this page, 9 on the next) Recall the n-BuI prep: acetone
n-BuBr + NaI ——-————-——>—- n-BuI + NaBr+
MW = 137 FW = 150 MW = 184
Q = 1.27 Q = 1.61 (a)(4) Suppose one is confident of obtaining a 40% yield and wants to get at least 30 unKﬂ.n-BuI. Calculate the minimum mass
(in g) of n—BuBr (limiting) which one must use to assure this
result. 30mw{g_~€ut
@ Mm! 3:543" WM " m
\2 7(MMl “‘34 6V MMolﬁﬂ/zv — -‘ (b)(2) Circle one phrase: Acetone helps the reaction by solvating-- the Br in n-BuBr so it leaves easily.
the I in n-BuI so it bonds easily.
the I‘ so it is reactive. e Na+ so I’ is reactive
the Na+ so NaBr can precipitate.
the Br‘ so NaBr can precipitate. N .
(1) n—Bu-Br ---—> g-Bu" + Br‘ +178 AGQLIi-GQ (2) NaI ----> Na+ + I' + 164 ‘4‘ ‘u (3) n-Bu+ + I" --—-> g-Bu—I - 171—] : -’0'q, (4) Na" + sr‘ --—-> NaBr - 174.5 (“l/w
Sum(Br): n-Bu-Br + NaI ---—> n—Bu—I + NaBr - 3.5 K ~200 The 91:131.]. energetics were calculated assuming that the net,
effect of the solvent acetone was negligible. This is likely
correct for the sum of rxns (1) and (3) . But for rxns (2) and
(4), taking account of ionic interactions in the solution
saturated in both salts gives a better estimate of 45. (1)(3) The sum of rxns (2) and (4) is—- NaI(s1d) + Br“ _.‘_____> NaBr(sld) + I‘ The solubility of NaBr in boiling acetone is 7.8 x 10‘4 M. Calculate its Ksp, = [Na+] [Br'] (assuming it is a 1:1 electro-
lyte) . Then calculate [Br‘] in soln for [Na+] = 1.0 M (the approximate effective [Na+] in acetone saturated with NaI) . Ksp = 7-3-1044)": 4.1 mfg-v
1‘ [Def Ker”) :7 Eﬂr‘] MW“CL% 1M«*= (2) (3) Taking cones of pure solids as 1, write an expression for Keg,
then calCulate its value,- take [I'] = 1.0 M. K _ If? ’ t Legit/0"
“7 ' [er—:1 NW0"
@2 (3) (3) Calculate A5 = -RT(ln Ke ), or = -2.3RT(1oglo~Keq), taking RT
= 0.66 kcal/mole. Does t e result mean the AGoverall is more
favorable with acetone as rxn solvent, or without it? (9 Ag = -2-3,<1’/o ,0 0.07405} ...

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- Summer '07
- Jung
- Solvent, NaI, Trigraph, dilute acetone soln, aq soln, Calculate dP/dT