CHEM_235_Sample_Final_Exam_-_Solution_Key.pdf

CHEM_235_Sample_Final_Exam_-_Solution_Key.pdf - i ‘...

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Unformatted text preview: i ‘ *. CONCORDIA UNIVERSITY — CHEM 235“ 'fi’ PHYSICAL CHEMISTRY II: KINETICS OF CHEMICAL REACTIONS SAMPLE FINAL EXAM NAME: DR. PESLHERBE STUDENT ID NUMBER: N/A . You are allowed a two—Sided formula sheet and a calculator. 0 Answer all questions on this exam booklet. 0 Show all working steps, as there will be no partial credit for guessing the answers. 0 There are 6 problems, the exam is worth 50 points and you have 3 hours to write it. . Return this exam sheet and your formula sheet (with your name and student ID number clearly written on both of them) at the end of the exam. 1. Pharmacokinetics involves the determination of the rates of absorption and elimination of drugs by the organism. After intravenous injection of a drug, the plasma of a patient was analyzed periodically and the drug concentration was measured as: t (min) 30 60 120 150 240 360 480 c (ng.cm'3) 350 311 206 146 75 30 12 a) Determine the order of the elimination reaction. (3 pts) b) Calculate the rate constant and half-life of the process. (4 pts) C) Comment on the results you obtained. (2 pts) 09 The concentration decreases by hat? or so Fvon‘n 6a to 150 min ) and again from ISO to :40 min . 'THL kadFaLWe. («‘30 min) seems to be 3ndep¢nA2r¢ or em conmfimHo") WlnCd-t suggesks Fiat-under k‘MHr-s Acm'w ) we. will plat: QA‘LCC) VS. t . Page 1 of 15 b) tank) 3:: .60 :29 15o Qua 36o gm :3 350 an us It’s #5 3o 12,- ,lec) 5.35 55H, 5.331433 n32 3.!40 2A8, 3o 60 120 I50 Me 360 11.80 ‘2 RM c :: Pm Co .. Kt. , 586-2% ._._. 7.5 \o" man" A89 .. Bo Nol’c: Men: 6.0% % ca: 14140 0%.cm‘3 R : .551on 2.. 31-- H’afifruct ti]: =; 3%:- = 9'5 m'tg c) M drug i? egiémal’ed 3;“th (had? J} in Se: mm) and Hue-e ts games? none. Lea: aflcx- 2, hrs (‘ng m'on). Pawn shouRA Hans Lake. Hw- deug twice. or Hat-ea. hm adpy. Page 2 of 15 2. Derive the rate law for the decomposition of ozone 2 03 (g) —> 3 02 (g) on the basis of the following mechanism, under steady-state conditions: (5 pts) 03 wt“ 02 +0 k1, K1 03+0902+02 k2 Under what conditions is the kinetics simply first-order with respect to 03? (2 pts) . Into—mama. 1 O autos-S =3 R4 [otlLol-F K1LO3-XEO‘1 (A) [0] c 2410214: 9oz. [033) ll 123$ == —- 92. $031 + kloiito‘i .. fiztomcil dit- "-'-" (- KtEO'AEO-l -- flax-031331) + RJLO-flufl— 942. [033153 moldng us: cf eq. (A) above- Page 3 of 15 aha makCc-is 0L5: 0F 9-“. C6) m :. £19.. [03-32- [5:011 + a, [053 mm. adtoz') << 1%,, [031 (0' IV ,3 _?—.._g‘ "E .03 .11 2:- &‘ E03] Note: 1? 49L” is smaflfl C fidto'zl << k‘to‘g‘l) H10. reachépn Proceeds as 'I‘ “‘9"- “’2’" no back f-QACELOn. in H1 fiv'rs‘r Shep) ”and Hm 9.03 3.x, so; Page 4 of 15 3. Use simple collision theory to calculate the rate constant at 200°C for the reaction: CH3 + CH3 —) CzHe Assume that the energy barrier for the reaction is O kJ.mo|‘1, the steric factor 1, and the collision diameter 4.0 x 10'10 m. (6 pts) Note: the masses of C and H are 12 and 1 gmof’, respectively. R PCs-8 55"” ll Pal Eu: 0 32:5de q- _._- we'- d = 1.. Io-‘c’ m = 5. \o"‘3 .m" Page 5 of 15 pt :2. 5.8 |()"‘6 = 3.5 lo" “.1 3.5 ‘0" Page 6 of 15 4. The following Lineweaver—Burke plot was obtained from the rate (v) data for the action of an enzyme on a substrate (8) at 20°C, when the concentration of the enzyme was 80 nM. 1/v(uM"s) Determine a) the maximum velocity of the enzymolysis; (2 pts) b) the Michaelis constant; (2 pts) 0) the turnover number; (2 pts) (1) the catalytic efficiency of the enzyme. (2 pts) Page 7 of 15 Mikael}: - Make“ ktmhcs "' (\me Arm: “I“ UNA/[8’3 \‘ KM __ I —_ 1 ______ .+ 3 °' 3‘5”” Armt'l ..—. - 4f :- ‘ :2 ol FMS MK CL) ArmM ' 12215 5) fl '4: 5\OP.Q‘:.. 0. Km "-'-' 0.128 .5 K lo ”145' J I .. “an“ : IO MMS c.) geek =1 I.28 EM 6 .1 \o. lo- Ms ”—_'ZB—" '3 2:.ch 80m M [E o PQCaE 1:. I25 5" Page 8 of 15 The rate constant for a unimolecular reaction is 2.1012 3‘1 at 25°C and it is exactly twice this value at 60°C. a) What is the Arrhenius activation energy of the reaction? (2 pts) b) What is the pre-exponential factor for this reaction? (2 pts) 0) What is AG* for this reaction? (2 pts) d) What are AHi and A8* for this reaction? (5p1‘s) Note: Assume a transmission coefficient of 100% 9a,: ELJO‘Z s-‘ 1": 9.5%.: 2‘58K 9L1: L‘JOW' 5" T1: 50"; :- 833K ,EoJ T Q.) R: A2... R a, e‘u-Efl/RTI .- ! 9&2..— e‘u-EaL7KT1 2/ 1..-}... ¢=> é." /R(-rl T1) = .1... 2.. --...E&..'.L....‘,_ .. ,L=_i2m9/ ® R T. T: .— M2. 1 _,\ E :2 .L_._..._. é=‘> CL RSI/7x3; (Tl T?— Ea: 8.3l‘l45 '3‘.mo\“ K"x%9/ : [63km Tmoi" ‘ _ — 1‘58 K 333K Page 9 of 15 I .JG'S 3mg" : RM; 5' x a smu'swmoi-‘K-‘xzssk l-QG ‘OIS S". A "‘ RT 9) 3. : 'kOT e: G/ P» e...AG*/R'n ... E. R 935T; Aer: .. RT in, 32. 3» ‘_ 'kJ. Axe": .. 8.31:..5 'SK"mo\" x 253 K x gm (2' IO'ZSJ ‘ 6,6262 16"" 3"; 1.53 10"“ 8K“ :1: 298K 2: 2805 3010‘" A6“ = 2.8 R'Jmok' Page 10 of 15 ) d) Lln'wn oLecvsLILr Madden AH“: 53“ _. RT “AG": R 9?. z: E. e. / T 133*. A}-}“§...'I‘AS"= ~£§T aAsi/RQ .HLAH +RT) /RT W W A a... EQ/RT .. 8.31.15 Triad" K" x 2‘58 K 16.39 .955 ma‘" .. 2.144 #:5de 13.2%?- k: mo\" I] )I Page 11 of15 153*: 8.3ms Tmo\"K" K Q— \.'58 ”“316“ x 298K = 3:,“ 3m"'K-¥‘ at am (”146 lo'5$,u 6.626210’SQJ'S ) Note: lei us Check wheH-u— ‘Hv. caQaAQakeci proPerlrLu are cm§tskent AC3: aHi T. 53* =: ‘3.8"} k3.n~o\" .. 9—958 K K 3:)“ Imo‘" K“. :2 13.87-1- 913'de ”.03 QT and" -"-‘- 2.8 bmd" Sam restate-k as .m qu-QS‘LOn C). Page 12 of 15 Isotopes and isotopic substitution are common in chemical kinetics. Here follow two applications: a) The 14C isotope undergoes (first-order) radioactive decay by emitting [3 rays, with a half—life of 5730 years. What is the age of wood in an archaelogical sample that contains only 65% of 14C. (4 pts) b) The base-catalyzed bromination of nitromethane is 6 times slower upon deuteration of nitromethane. Explain and account for the observed effect of isotopic substitution on the kinetics. (4 pts) Note: the 0-H force constant is 450 Mm", the masses of C, H and D are 12, 1 and 2 9mm”, respectively. Page 13 of 15 b) 9;”an kiln-ah: ”01130.2 afFQCES I}? H1!— Cleouraga cf aL C...H vs. (3...!) bond. KCc—H) __ 8.7% RCCJD) ‘- Page 14 of 15 ° \ E‘ " ERR» ‘ :1 i 6.6262m'3" 325 x 8 6L, 10:35” 3 3.86 Id.“ 3' A: ~o.9_'?x2486lo'u3 =1 ..|.38 L3?) \o'tst.\_238K {:(¢.__‘__:_R) f—kaw 6,5 9:0; 9) ._..__._. 'Tkts ls consxstexi' wfi'P-u what: observed; fixpenmmbfifly- Page 15 of15 ...
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