105bf07_key_e1

105bf07_key_e1 - Chemistry lOSbL First Letter of PLEASE...

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Unformatted text preview: Chemistry lOSbL First Letter of PLEASE PRINT YOUR NAME IN BLOCK LETTERS 1 1:00 am. Section Last Name Fall 2005 Name: EXAM #4 November 22, 2005 Professor Arieh Warshel Please Sign Below: [certify that I have observed all the rules of Academic Integrity while taking this examination. Signature INSTRUCTIONS: 1. There are 5 problems on 8 pages in this exam. Please check to see that you have a complete exam. 2. Please show all of your work to receive full credit. 3. You must use ink. Do not use a pencil. Answers written in pencil are not eligibel for regrades. Useful Physical Constants and Equations: Avogadro's number N = 6.022 x l023 mol'l Universal gas constant R = 0.08206 L atm K“l mol" = 8.314 J K" mol‘l Faraday's constant F = 96,485 C mol‘l TK =TC+273.15 Rate = k[A]” [B] ”' t 1/2 lst order Rate = k[A] 1" [[Ale' = kt 0% 2nd order Rate = k [A]2 % ‘ fi = kt HAT 0th order Rate = k [14],. ' [A] = k’ k = Ae—amr 1. (20 points) The following data was obtained for the reaction 2N0 (9+0: (g) —> 2N02(g) Experiment [NO]o [02] Initial rate (moi/L) (moi/L) (mol/L) [moi/L sec] ——-mm 1-0 x 10" 7-0 x W 2.0 x 10-3 1.0 x 10-3 ‘ 28 x 10‘ a. Determine the rate law. Show your wont. b. Detemlinee the rate com - E fi/SW’ =- iKIk/OJMYOMQ)’ Ike: 8—1 .5 (27900.4) 1‘” c. Determine the initid m for up“ 4. mt: (vyifl/S”)(90X’33L[5‘°§/flj f : '—"'”‘g7gx/b’é/4 s" 2 gem/$3957 '4.- *~-- 3 2. (20 points.) The reaction exhibits the rate law Which of the following mechanisms is/are consist for all the four mechanisms. 3. NO + NO + F: —> mm b. NO+F2—> ONF+F NO+F —-) ONF kl NO+ NO 2? N202 k4 N202+F2 —> OZNZFZ N202}:2 ——> ZONF F2 —> F+F F+NO —> ONF F+NO —-> ONF 2NO(g) + F2(g) —> 20NF(g) Rate = k[NO][F2]. ent with this rate law. Explain your answers 12,019 1 ll [N 9322. PU ho goal} slow {- Hod}: 1: l’limljlwi-jj‘] fast fast for both kI and k_l Slow WW A ads ’1. \1 302 fast 3 all) :: if] '3 2 1i kt. [40) A M9: 31)}: - 0 A' '2 k”, M lug} slow “a 9’39“) fast W fast ,{ fiwz‘lpaj Mn 30,”; (b) (20 points) Circle "true" or "false" on the following questions: (i) The half life of a first order reaction does not ‘ depend on the rate constant. True (False) (ii) Pseudo first order reactions occur when some of the reactants are at a very high concentration. 611% False (iii) The integrated rate law gives the dependence of "\\ the rate on the time. True @e' (iv) The activation energy can be changed by catalysts. 611;; False (v) Arrhenius studied reactions at different temperatures. @ False ./ False An enzymatic reaction involves an attack of RO' group on a peptide bond after a proton transfer from ROH to B', i.e., (vi) The elementary step A + 2B ——> C is therrnolecular. ROH+B L/c==o ——-——~R-—o'+afl:/ =o———-. BMW n—o— —-o ‘ / / RS Tg 0) Could the enzyme accelerate this reaction by an active site of the form (circle "yes" or "no" and defend your answer with an explanation)? An active site that freezes the motion Yes 60 ) Explanation of the reaction fragments and use an I v r) W 5 as 0i entropic effect. M to ) \Ij w p (ii) An active site that pushes R-O-H towards the >C=O. - Yes @ Explanation $1104 J0?) max I L MW Hm)” w 51mm?!) (iii) Yes No Explanation @ glob/012.01 “V Cir-4).w T1 (iv) 6% No Explanation SivNQZ-J’J CH0 ‘ "TL! ' 4'4. QCpoint-s) ' ~ ‘ (a) The reaction A—) beCOmestet-i times faster when the temperature changes from IOO"C. to 200"C.‘ " What is the activation barrier Of this reaction? V ‘ $ _ 3‘53" K—z I! i‘ 1 ' >3 '1? Q « NA ,_ :Ii- '- \/ , 9:73.373 Ed: _(2‘393—Y(g,3m]m“ih'n) ‘ “W‘s-cane kn 3'3, K H w” ' (b) If the rate of the above reaction is 1 M/s at IOO'C, what will be the rate It O‘C? ante/(Wu fossib/c -— u‘~/A4r so/Ve 14v- A £4," 7‘2/1-9‘C. M flu? IPrIo (3444:9071, 14v 7"=o'c/ or Mmfib £10 .2 ez—omfim M #5_W. _ 35.8x/o 3-03.06 / 73 (J Ratio?— ch 5'5’“5K"7( 75" 275K__ Rafil ’ —33.8X/o’ TM" "‘ __/ “I e (3.3NJ’K")(375K) / M S Rafi e2: [SW/0’21! s" A/ I 24:514/2: /o 44.97 --2 - (c) What will be the rate at -273.15°C? M m m 2 3 954”, £15! Zen. 4% aééo/zde zero [0/01 a“ mfim ceases (177 dcgé'yfinl 5‘ “M”? “Mo‘f’ 6% 4n? mwfi‘m. 7 5. (20 points) (a) Consider the following initial rate data for the decomposition of compound AB to give A and B: [AB]0 Initial Rate / / A330 1/1 0 ’ (mo ) (mol/L s) {1' 4/ 0.200 3.20 x 10'3 0.400 1.28 X 10'2 0.600 2.83 X 10'2 Determine the half-life for the decomposition reaction initially having 0.8 M AB pr sent. -} I X 12,152 _ [2,8x/o = __ 0400/3 x R515} - 3.1%" 4 ~ 0.24941 = '2 =>X= '2 (2‘1 ova/er rm) m 4» 74.14% R£¢=Jé [453‘ '3 ~/ ._ 1: R43 3.10100 41$ = 0.08”! _, [pt-57’ - (along); '61 3"“— ="‘——\ = /5‘.éu¢ v ACABJO (o.osy‘&"){o.8d) (b) Derive the half life for a zero order reaction. (Show your work.) [Al - [1+] _= Jui- @ [A], .- wi wig ...
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105bf07_key_e1 - Chemistry lOSbL First Letter of PLEASE...

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