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Exam 1 CHM 104 - NOTICE This Material may CHM 104 Be...

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Unformatted text preview: NOTICE: This Material may . CHM 104 Be protected by copynght law Rob McGaff l3 .._ 8 (T1tle 17 US Code) Fall 2007: Exam I (form A) C LU: lnstructions: . 1. This exam consists of six pages and a periodic table. If a page is missing, notify your instructor immediately. Be sure to write your initials on every page after this one. 2. The exam should be completed in 50 minutes. Budget your time, and be sure to answer the questions you know how to work first. Part | is worth 48 points. Part II is worth 23 points. Part III is worth 29 points. 3. Record all multiple choice answers on the key below. 4. Try your best, and good luck. . multiple choice answers: 1. a b c 63 e f 2. a b c ® e f 3. a b©d ef [email protected] A ’ d C l: 5 Part I: Multiple Choice. Read the questions carefully and examine all responses before choosing the best one. Circle your answers, then mark your answers on the key printed on the cover page! Only this key will be graded. Twelve questions, 4 points each, 48 points total. 1. In the following reaction: A(s) + 28(9) —+ C(g), which of the following can reasonably be expected to increase the rate of reaction? * a. grinding A into a very fine powder / b. lowering the temperature 0. raising the temperature @ a and 0 above e. b and 0 above f. none 0f the above 2. For the reaction X + 2Y + Z —+ Q + R, the rate law is found to be: Rate = k[Z]. Given this information, which of the following must be true? a. Z is the only reactant in the rate-determining step / b. X and Y are intermediates c. The reaction has at least two steps / @a and 0 above e. b and 0 above f. none of the above 3. In the reaction 2X + 3Y —¥ 2Z, Y is being consumed at a rate of 0.30 M -s-‘. At this point in time, the rate of reaction is: a. 0.30 M-s-1 b. -0.30 M-s-1 l2 _ ‘_ It ( b [“1 @010 M-s-1 ME — 3 rye d. -0.10 M~s~1 ~ e. 0.90 M-s-1 _ .t\ l ,_ . f. noneofthe above ’1 — :3 C 0.30M S 4. The reaction CO(g) + Cl2(g) —> COCI2(g) occurs in a single step. From this information, which of the following are possible units for the rate constant? a. MS1 S€C¢~D ORWFZ. e. M-Zs-2 f. can't determine/ not enough information is given F1459" 02- D C ’7‘ 5. For the reaction 2X —> Z, the rate constant is 1.3x 1 5-1 he time required for [X] to drop to 25% of some initial value is: a. 5.3x104s . 0qu (831.1x10-3s “(31' 7.. (Set/2) : 7.61,; 3 c. 2.65x10-4s d.1.3x103 _‘ e. .6933 _ f. can't determine/ not enough information is given 6. Catalysts: a. increase the rate of a reaction by increasing Ea @increase the rate of a reaction by decreasing Ea/ c. are consumed during the reaction d. a and 0 above e. b and 0 above f. none of the above cl—cl'C—C‘ fowl; Q‘ECC'J‘Q an, ‘91-: K k 7. in the reaction 2X —+ Y, k = 1.2 x 10w [X] = 1.2M, the half-life of X is: . o _ a. 96.3 mm 116 min ' ”[7 ‘ c.1.44x10'4s I : __ E d. 1.2x10'4s I2. kEXL ” e. none of the above are correct 1 f. can't determine/ not enough information is given “7. ‘_11IO,L'M.-1§-| 0 .1 M\ 8. For the reaction H2(g) + l2(g) 1? 2Hl(g), which of the following actions will necessarily shift the reaction to the left? / a. removal 0ng b. removal of I2 / c. removal of HI NC) 6 d. addition of H2 Mo ————\ @ a and b above ' f. c and d above 9. For the reaction Y + 22 —> A, the rate law is found to be Rate = K[Y][Z]. A possible rate determining step for this reaction is: @wza Q d. all of the above e. b and 0 above 1. none of the above 10. For the reaction N2(g) + 3H2(g) S 2NH3(g), which of the following are necessarily true when the reaction has'reached equilibrium? a. [N2] = [H2] = [NHa] [U0 b. The toward and reverse reactions stop N 0 C @The forward and reverse reactions proceed at the same rate ME j / d. a and b above e. b and 0 above f. none of the above 11. For which of the following reactions would Kc: KP? @Mg) +|2(g) :2HIIg) b. N(g+3H (g) r. 2NH (g) _ L (L c.'2t2:(s)+ 022(9) :: 2003(9) \AP — Me, CO 0%?“ )9 w d. all of the above e. a and 0 above 1. can’t tell/not enough information is given 12. For the reaction CH4(g) + 202(9) —> C02(g) + 2H20(g), the rate law is: a. Rate = k[CH4] ’ b. Rate = klOg]2 __F 0. Rate = k[CH4][02]2 d. Rate = k[CH4][02] e. k = [CH4][02]2 @Can’t tell/ not enough information is given v lb hé~0x."C.'Ct———‘P Part II. Short Answer. Answer the questions in the space provided. Three questions, 23points. 1. {9} Consider the following reaction: A + 28 + C —+ D + E Using the data shown below, write the rate law for the following reaction: Expt. [A]o ' [B]o [C10 Initial Rate (We) 1 0.0500 0.100 0.100 1.2x102 9, Q 12+me 111% E2 0.100 0.100 0.100 2.4x102%CX Fir-6M“ 3 0.0500 0.100 0.200 1.2 x 10-2 [3,1 L04 0.0500 0.200 0.200 4.8 x 10-2 QATE‘W RATE LAW: RATE : k {Q {1311— on coordinate diagram for the equilibrium reaction X+Y ‘— Z, for which Kc- — 1.3 x 10 2?- B sure to label your axes and show Ea' In the fonNard direction, the reactants, and r0 uc on your diagram. RXN. PROGQ: $3 3. {4 each} Write equilibrium constant expressions for the following: a. 2802(g)+02(g) S 2803(9) E303]? c= [SQ/11102.] b. NiO(S)+CO(g) S Nl(5)+002(9) ice j '2. [£01 Section III. Problems/ calculations. 'You must show all of your work to receive credit. Your reasoning must be clear. Draw a box around your final answer, and don ’t forget to express your answer in the proper units and to the proper number of significant figures. Four questions, 29points. 1. Cyclopropane, C3Hs, rearranges to propene in a first-order reaction: cyclopropane —> propene Til—z. __ (J. (ft: \4 : C; ‘03 : ELI/HOW)“, The half-life for this reaction is 12.8 h. lg “CI/1 a. {4} Calculate the rate of the reaction when [cyclopropane] = 0.545M RATE, '7— )L [chtcprchgr-tr] ‘ : Bun/01k” qu‘v‘mj : liqs’xlo‘t Ml“ l b. {6} Calculate the amount of time required for 29% of some initial concentration of cyclopropane to react by this process. ( lCHCLc/Pnopnrd‘t 1 r G 3" Emacajg 1M ($1.) it 5% ,(gfim :H AGES: "JV 03%.? : titulfloik" (fl 2.{5} For the reaction X —+ Y, a graph 0% vs. 1/T yields a straight line with a slope of -1.23 x 103 K. From this information, calculate Ea. La SLOPE: “LEE— R a: ._ gLon Ln.) : L23 x103l4 {8.3% T «at K 5 E ; erlflot‘S“ __. pare? 3.{7} Forthe gen ' reaction, 20 -> P+R, the rate constant (k) is equal to 2.5 x 10'3 M‘1 5-1. From this information, calculate the time required for [Q] to drop from 2.42M to 0.52M. Show all work. L; _l_ 2:33” $531.3“ .LML Lttfgfi 9&1? _L t i fih '— £6532» M k _ I _ l “ 6.91M Z-‘DM A 2.?$Io*3[~1"$" P 4. The following equilibrium process has been studied at 230 °C: 2NO(g) + 02(9) : 2N02(9) In one experiment the concentrations of the reacting species at equilibrium are found to be [N0] = 0.0542M, [02] = 0.127M, and [N02] = 155M . a. {3}Calculate Kc for this reaction 2 2- C'— lécv Loot—1 M [”17] [551131221 _. LO.CELIL]LEO.ff-i3 ._ __.._..4_._._~~--~—- -~~w-_....._...__ V10 : 4 . Lilly )0 5"“ t c. {4} If 1.2 mol NO, 1.2 mo 2 an 1.2 mo 2 are introduced into a 0.500 L vessel, which direction will the reaction run? You must support your answer with an appropriate calculation to receive credit. ‘ _ [~61 : [021:2wa1 : £601 «*1 ‘l V\ (await? < 14c. x 0 mxm. $2qu (551:? To RIG-HTC——B\> 00/ CHM 104 Rob McGatf Fall 2007: Exam|(torm B) Cé—‘TLE’EM B Name:_}fiL+ instructions: 1. This exam consists of six pages and a periodic table. If a page is missing, notify your instructor immediately. Be sure to write your initials on every page after this one. - 2. The exam should be completed in 50 minutes. Budget your time, and be sure to answer the questions you know how to work first. Part l is worth 48 points. Part II is worth 23 points. Part III is worth 29 points. 3. Record all multiple choice answers on the key below. 4. Try your best, and good luck. 1 a c d e f 2 a b c d @ f 3 @ b c d e r 4 a b 6) d e f 5. @ b c d e f 6 a b c d e Q 7 a b c d‘\ e f 8 a b c G) e t 9 a b @ d e f 10. a b (3) d e f "11. » a @ c d e r 12. _a ® c d e t b~~c~2 ~oc~c~no-‘F .1~d~.c~~C-b'\h 7. In the following reaction: A(s) + 2B(g) —> C(g), which of the following can reasonably be expected to increase the rate of reaction? a. grinding A into a very fine powder b. lowering the temperature c. raising the temperature / @a and c above e. b and c above A» f. none of the above / 8. For the reaction X + 2Y + Z —+ Q + R, the rate law is found to be: Rate = k[Z]. Given this information, which of the following must be true? a. Z is the only reactant in the rate-determining step / b. X and Y are intermediates ms """" cThe reaction has at least two steps M d @Da and 0 above e. b and c above f. none of the above 9. In the reaction 2X + 3Y —> 22, Y is being consumed at a rate of 0.30 M 6". At this point in time, the rate of reaction is: a. 0.30 M-s-1 b. -o.30M-s-1 , ._ _ _l_ A 011 C, @010 M-s-1 R’W“ S ( d. -0.10 M-s-1 I e. 0.90 M-s-1 _ _.'__ .2] f; none of the above “— 3 (1‘0 30 M ‘ g B 10. The reaction CO(g) +Cl2(g) —> COCI2(g) occurs inasingle step. From this information, which of the following are possible units for the rate constant? . H {b oft O‘C a. M -s-1 S ECO {k f. can’t determine/ not enough information is given 11. For the reaction 2X —> Z, the rate constant is 1.3x 10391. The time required for [X] to drop to 25% of some initial value is: 5.3 x 10-4 s .1x10'3s f: thWd : 1 < 0:51”? c. 2.65 X10‘4 3 d. 1.3 x103 e. .693 s f. can’t determine/ not enough information is given 12. Catalysts: a. increase the rate of a reaction by increasing Ea @increase the rate of a reaction‘by decreasing Ea / ' c. are consumed during the reaction b d. a and 0 above e. b and 0 above f. none of the above d~c1~C—C*ib“b . ‘ 3 Part II. Short Answer. Answer the questions in the space provided. Three questions, 23points. 1. {9} Consider the following reaction: A + 28 + C —’ D + E Using the data shown below, write the rate law for the following reaction: Expt. [A]o [B10 [010 Initial Rate (M/s) % 1 0.0500 0.100 ' 0.100 1.2x10-2 [0]” that A 7 Lglk [:2 0.100 g 0.100 0.100 2.4 x1023 ' 3 0.0500 0.100 0.200 1.2 x 10-2 95-” L [s 4 0.0500 0.200 0.200 4.8x 10-2 ~ A raw ~ ‘3 @04ny 3. {4 each} Write equilibrium constant expressions for the following: a. 2802(9)+02(g) :. 2803(9) [$037 ‘2 Kc = Be? 201] b. NiO(S)+CO(9) *4 Nils)+002<9) Kc: 3: A [Co] Section III. Problems/ calculations. You must show all of your work to receive credit. Your reasoning must be clear. Draw a box around your final answer, and don’t forget to express your answer in the proper units and to the proper nu i nificant fig es. Four questions, A 29points. .\ '5‘ _. C; (9‘13 ,V k _ 0 m3 1. Cyclopropane, C3H5, rearranges to propene In a first-or Aon: ‘4 t”). : 61-6133 cyciopropane —> propene M L —_-_ C..“1C,L0Pt"2 ”6 Kirk The half-life for this reaction is 12.8 h. ' : fillioifi—l a. {4} Calculate the rate of the reaction when [cyciopropane] = 0.224M W1 ~~ ~ i4 {q 2 ; Jami/0’1 '[o lidfll Izr‘xIO'LM l" b. {6} Calculate the amount of time required for 14% of some initial concentration of cyciopropane to react by this process. [C1 : CD gé i111 ca /IM (03%;) : lc—E I : OJEI I; (fix/01%" 2. {5} For the reaction X -r Y, a graph okk vs. 1/T yields a straight line with a slope of -2. 44 x 104 K. From this information, calculate Ea. Jive 3.71;: cap-«o carat/V 3.{7} For 0 reaction, 20 -> P + R, the rate constant (k) is equal to 1.4 x 1Wm—L— this information calculate the time required for [Q] to drop from 1.33M to 0.44M. ow all work i— » -t 12% C05] ‘ [(3)10 _L_ _ .L rt “- E41 [671,] _,L- ‘17 ”£153 V [(R15 i ‘l i J— ,L. 7:- : I O C} >70 I Z: OW” - 1:3?” .35 / é E ‘lgqylcd'IM—lsbf : 2%1MT‘4 f 4. The following equilibrium process has been studied at 230 °C: ._.. 3 C1 \H 2NO(g) + 02(9) r. 2N02(g) —-~~- ~ in one experiment the concentrations of the reacting species at equilibrium are found to be [N0] = 0.0542M, [02] = 0.127M, and [N02] = 15.5M. a. {3}Calculate Kc for this reaction . fi V2 {wozji - gig 51L C. : "' . 320122053 {0051237501133 lé ._ : é. 4 4 m 5 c. {4} If 1.2 mol NO, 1.2 m 2 and 1. 2 mol N02 are introduced into a 0.500 L vessel, which direction will the reaction run? You must supportl your answer with an appropriate calculation to receive credit. {7&1}le Bag] “:02? (5‘02”): 0 922‘, [mil 71:07,] :1. M o aw. chg LEFT 7o RIGHT ...
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