chem1B-Spring_2009-mt1-Saykally_Lester-soln

chem1B-Spring_2009-mt1-Saykally_Lester-soln - Chemistry 1B...

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Unformatted text preview: Chemistry 1B, Exam I Name ' l; February 18, 2009 Professor R.J. Saykally TA 1. (20) 2. (15) 3. (20) 4. (10) 5. (10) 6. (10) 7. (15) TOTAL EXAM SCORE (100) a dt 1) t c t d dt 6 = CO e”" t 2 1n_ : 0.6931 1/2 k k l = i + 2k! 0 c0 k :Ael RI ln k = In A — YET d[P] _ _ k2[E] [S] 7 ‘ MES] [S] +0Km Rules: Work all problems to 3 significant figures No lecture notes or books permitted No word processing calculators Time: 50 minutes Show all work to get partial credit Periodic Table, Tables of Physical Constants, and Conversion Factors included Chemistry 18 8’09, Exam I Name 2 1. (20 points) The mechanism for the decomposition of gaseous NOzCl is In NOzCl H N02 + Cl k—1 k2 N02C1+ Cl _' N02 ‘1' C12 By making a steady-state approximation for [C1], express the rate of appearance of C12 in terms of the concentrations of NOzCl and N02. mica: "LEE; .— LZ Lp’ol “1:011 awn-«rm» g r fiifixtfiyiic34fik M251] : \L. i: M01 L\F1 ‘ \é _\ E5901 lLCZi’l — k1 Cubic (LEG): :0 M \é. [2 H01 («71 ‘aé __‘ [MG-2,1 [053 t‘ \‘QENCLO—J [(41 "\o‘ [N021 '4 V1 i: N501 Obi ’L. 4 cng r (4. t2 E Egg-Ci 4 r (L 7, [N011 + timer-gm] 2. (15 points) A certain first-order reaction has an activation energy of 53 kJ moi—l. It is run twice, first at 298 K and then at 308 K (10°C higher). All other conditions are identical. Show that, in the second run, the reaction occurs at double its rate in the first run. ‘Ew/K‘x“ _, L“ /(3 V2 iL : AC | L1 2 AC. “Emlm LL Ac ‘“ _ Aux/(1h )4. he ) 2 _ £9. 1 Lb zQ/‘A \L‘Z .'/\ kI (<T1 (Q _\_.| .1 _ D343 iJ-mfi—‘x H552)" \LLI)” + $373 y).mui‘- [djg‘yus‘ rvw'l ‘6.3xL\.>wv--a\“ r352 ‘ ma 37 .‘nui“.yi",gsfig L Vi¥}\ - 405cm 2 oven 7 0&4“; JCA L. ,- " 1;? “ * 9.00 Chemistry 1B S’09, Exam I Name 3 3. (10 points each) Certain bacteria use the enzyme penicillinase to decompose penicillin and render it inactive. The Michaelis—Menten constants for this enzyme and substrate are Km = 5 X 10‘5 mol L‘1 and k2 = 2 X 103 s". A) What is the maximum rate of decomposition of penicillin if the enzyme concentration is 6 X 10‘7 m? 5‘ [:7 ,1 : LIKES] T k1 [.2ch8 l ‘Ll/ L53 3 KM A - ‘ \ \n ‘ ‘ . ' ‘r "’ '. 7\1'0"‘—\‘\0 ”\- Nmmrv\‘wvv\ (0—H. (1293.“th Vic‘s“ a4l.“a\‘r+ LmLLN t CS1>7KM [F " , ' fl L5 "" lifill .:»4§L£} ; ujil ‘ L NM L's, LI xv) , - .ui ffl/ ,./' ”3 .. 'lelD ml L S‘[ B) At what substrate concentration will the rate of decomposition be half that calculated in part (A)? . {42 l: {1 c [ 5] T J\ ”Pk K 5‘ ’6 W\0\\L (031" i Z [5.] 1 K M L153]; Lay/ELE‘Q L 1 ,,‘/--—‘—/'—i Mtg/”5”. (E517 {A \ Chemistry 1B S’09, Exam I Name 4 4. (5 points each) In class, we described the Lindemann mechanism for the “unimolecular” decomposition of a gaseous molecule, e.g. N205 + M -' 2N20 + % 02 + M A) Write the differential rate law appropriate for the reaction found at low pressure? A? low 'PFCQ‘DUu’tfi AMA rco UH on V: éeautcl — CWCL'J (“”3 l: Mfg “D U33 LU\\\'\ ‘)l L.) n u‘j “UK LL; lc‘x’l‘\C‘-\/‘\ (LS-ff?) , 7_ , ~ '2. -~ A W3 L mus. A C\ * B) Sketch and label a plot of the reaction rate vs. total pressure. row/hm MRO v/ .44" M C; M'WJMH‘T‘ “B‘Qb‘i—fl \\\/\/i\"\‘ \ \ CFCQN F k’ “’le p r c ‘= ">\.\ FL l" *‘ “Pig‘SL-H. \vaHi 2"“8 criU' r‘cd‘L Chemistry 18 8’09, Exam I Name 5. l (5 points each) Manganate ions, MnO42_, react at 2.0 mol-L‘l-min_ in acidic solution to form permanganate ions and manganese(IV) oxide: A) B) 3 Mno42‘(aq) + 4 H+(aq) —. 2 MnO4_(aq) + Mn02(s) + 2 H20(l) What is the rate of formation of permanganate ions? a ALE/«£13 1 _. “will \ What is the rate of reaction of H+(aq): '\ VL— \ CA I Ht} 7. ~ 1 Cl E__M A (-L‘ -1 -- a z: 3 43* (til 3 Li(QO rwfl' Lik- moi) h 3 ' 'i 1.13,} Mi'Lq‘Wxfi Chemistry 1B S’09, Exam I Name 6 6. (10 points) The rate of a particular reaction is found to decrease as the temperature increases by 10°C. What does this imply? Explain. The «when has flAQ'fi ch‘n cum abithmwfl w? ‘x f . “Vb“, - "i * :o/ @- ib me) an €/\€t/\/\in-\CV\1 Pm‘dTC/fl' m LR (“l ikwfinnl ML¥ “3 rmfisrg \g vdmlfck h 'k/‘WVPEFCJHAFQ H‘l We A (V.MATL\5 ("mecgbtmi \‘4 3 G: Ek/QT (by Don \é: OJ“ A ' EST) 7 \A; 5 {Wk (d: 3 ‘H'x—k V.CL"‘C O l (MN ek‘lxw-Lnr’xecfl/Y 11.0% a“ WW~ ‘5 '\ 0i p . . __ law‘s r ‘ ‘ r .— fl 9’ ' \ ("K a“ ’- 3\+\J’f‘ ) l/\ K (TREE, W .‘_\,{,\ m affix (:9) Tim? (recluff. \ _,\( lg." .\ | . f“ 7. (3 points each) Short Answer A) The total world energy consumption is currently about )3) “ \Y‘) Terawatts, and about f“ 2 % of this energy is currently produced from chemical reactions. B) Two types of chemical explosions were demonstrated in class. Specify these types and give an example of each. 06 N15) ( c" Lo! \c'o A w.'w\a-\x¥ fiV'w C) Rates for chemical reactions with low activation energies that occur in liquids are d ( ting-.00 limited. ...
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