chem128 ExamII Sum03

chem128 ExamII Sum03 - CHEM 128 (Maxwell) Exam II October...

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Unformatted text preview: CHEM 128 (Maxwell) Exam II October 30, 2003 This exam represents only my work (signed) _ 7 U W, Good Afiemoon! Relax and read each question carefully. I will try to clarify any question you think is ambiguous or lacking information you thought would be provided. This exam consists of 22 questions and the expected data pages. Be sure your exam is complete. Be sure each numerical answer has the correct number of significant figures, is labeled with the appropriate units and if appropriate, put into scientific notation. At some time during the exam period, review th xam so that u an wer th uesti tha wi 1 et ou the m t ' ts durin the cam period. For everyogg’s comfgn, please keep those portions of your exam not in u c vered with n of ourd ta e . Than ‘llt .., Questions 1-16 are multiple choice. Circle the letter A—E that corresponds to the correct answer. (2.5 points each) Note, this portion is printed back-to-back 1. The gas phase reaction of 2 N0 + Cl; 9 2 NOCl has been shown to have the rate = [N0]2[C12]. If the concentration of NO is doubled and concentration of C12 is tripled, the reaction rate would be increased by a factor of A' 6 [23 T33 = h, B. 9 @12 . 18 E. none of the above 2. A catalyst is effective because It increases the number of molecules with energy equal to or greater than the activation migrants . . . B. It mereaseethe activation energy for the reaction % It increases the number of collisions between the molecules 2.} i It increases the temperature of the molecules in the reaction. 3. The reaction quotient Q, for reaction has a value of 5.43 X 10‘4 while the equilibrium constant, Kc has a value of 3.65 X 10'3. Which of the following statements is accurate (note resp nse E also)? The reaction must proceed to the lefl to establish equilibrium e reaction must proceed to the right to establish equilibrium . The concentrations of products will be much smaller than the concentration of the reactants when the system is at equilibrium . The concentrations of products will be about the same as the concentrations of reactants hen the system is at equilibrium. E. ore than one of the above are accurate. 5"”?3 (a YQHU) [/}< x l CHEM 128 (Maxwell) Exam 11 October 30, 2003 page 2 4. Sulfur-35 is a radioactive isotope which decays with a half-life of 87.1 days. What is the h -- t- t order rate constant for its decay, in units of days]? glen than 1500 x103 3 JL sh - £237 .1 _ B. 1.01X10' to 5.00 X 10' J . L/@S.01X10'3t01.00X10'2 87,! = £3.02 .. 121%. 1,, am “07° /" . 1.01 x 10'2 to 5.00x 10-2 4L ‘574 E. Greater than 5.00 X 10-2 . 5. Sulfur-35 is a useful biochemical reagent in some laboratories. It is usable as long as 14% of the original activity is present. How many days will the reagent be useful? The half-life of sulfur-35 is 87.1 days. . less than 150 days - “g 151 to 250 days xiii—m ‘4 ‘0 C. 251 to 350 days D. 351 to 450 days VQA ‘00 ; (7,qxto*?>t E. eaerthan450das gr t Y lLi t5 2c e reaction rate increases by a factor of 10000 in the presence of a catalyst at 25°C. The activation energy of the original pathway was 101 kJ/mol. What is the activation energy of flgy the new pathway, all other factors being equal? 4 O ‘ = ‘0‘ \r—J Am) I - = less than 70 kJ/mol ' T 1g ER. . 70.0 to 80.0 kJ/mol \o 0 00 WE ,3 N 101 i c. 80.1 to90.0 kJ/rnol E 4‘ ' L“ d “km” “‘3 /"~°'9( tax % z} @0110 100.0kJ/mol U, ( “1000) Q3 "INA LMQDBO _ 'E‘k __ / E. greaterthan 100.0 kJ/mol Ln ‘0' ' Lg‘ab‘Lwa-lxlqg3 /g{— AL [ \mgbr ZH‘W amt-WM 7. Consider the following statements and then make the correct choice. Tfi I. Decreasing the pressure in a gas liquid reaction would decrease the reaction rate. Tgb'rhe higher the activation energy, generally the lower the reaction rate. I and II are both true ‘lfl B. I is true, I] is false /9 @I is false, II is true D. I and II are both false 8. For a reaction with a rate = km]2 [B]‘, which of the following is not true about a reaction" having this expression? a . The reaction is first order in B 9 The reaction is overall second order ,2/ The reaction is second order in A /E.( Doubling the concentration of B doubles the rate 21’ all are true, or more than one is not true. ‘ Y quW 0 . CHEM 128 (Maxwell) Exam 11 October 30, 2003 page 3 ' 9. When a catalyst is added to a reaction mixture, it A. increases the rate of collisions between reactant molecules ‘ B. provides reaction molecules with more energy slows down the rate of the back reaction provides a new pathway (mechanism) for the reaction ’ . does none of the above 10. Consider the following two statements and then select the appropriate response (a-e). F I. At a given temperature, all molecules possess the same kinetic energy. a f“ 11. Increasinlg the concentration 03' a reactant that occurs in a step after the rate-limiting - step wil increase the observe rate of the reaction. A. Both statements are true B. I is true and H is false C. II is true and I is false Both statements are false 11. A reaction is first order in X and second order in Y. Doubling the initial concentration of X A and cutting the initial concentration of Y to three-fourths of its previous concentration at UN FINAL constant temperature causes the initial rate to by a factor between .____._—-_.=.— A. increase, .1 to 1.0 I f @ increase, 1.1 to 1.5 RICO. ' U" (W; C. increase, 1.6 to 2.0 [1] [37;] 1 [:13 C‘) d D. increase, 2.0 or higher E. decrease, .1 orhigher ‘3 W's ® ' -- - ' - .— FP—A-M Tamar. 12. The equilibrlum constanth, for the reaction PC13 (g) + C12 (g) —» PCis (g) at 239°C is 49. A rigid 1.00 liter cylinder at that temperature contains 2.9 atm of PC15 _ 0.70 atm PC]; , and 0.30 atm of C12,. Is the system at equilibrium? (9“ .5 t. Q1 -;“:. T" C15 J Yes ’ 4 1"] . 3 '2 fl No, the forward reaction must proceed to establish equilibrium. '1 or] C. No, the reverse reaction must proceed to establish equilibrium. \2 (5 r C D. More data is needed to draw a conclusion. Hp> Q I 3] 13. For the reaction A2 + 82 9 2 AB, the activation energy for the forward reaction is 125 kJ/mol and the AHom, = +35 kJ/mol. What is the activation energy for the reverse reaction? A. less than 85 kJ/mol @ 85.0 to 115.0 kJ/rnol C. 115.1 to 145.0 kJ/moi D. 145.1 to 175.0 kJ/mol E. Greater than 165.0 kJ/mol Blue sheet MC 1-16 Probs 17-22 Total CHEM 128 (Maxwell) Exam 11 October 30, 2003 page 4 14. Consider the following two statements and then select the appropriate response (a-e). I. The reaction immediately below is at equilibrium. A subsequent addition of NAD F would shift the equil' rium to the left. lactate (aq) + N (aq) S pyruvate (aq) + NADH (aq) 1 II. . The reaction immediately‘fi‘lfiv is at equilibrium. A subsequent increase in pressure of T the system would shift the equilibrium to the left. ' 2 N205 (g) S 4 N02 (g) + 02 (g) )( Both statements are true ,B/ I is true and II is false 11 is true and I is false D. Both statements are false E. Cannot determine 15. Consider the following two statements and then select the appropriate response (a-e) I. The reaction below is at equilibrium. A subsequent decrease in temperature would shift f the equilibrium to the lefi. {JAM C2H4 (g) + H20 (g) r. CHgCHO (g) AH°rm = —151 k] f 11. The reaction below is at equilibrium. A subsequent decrease in temperature would shift the equilibrium to the left. *W N204 (g) S 2 N02 (g) endothermic A. Both statements are true . _I is true and II is false 11 is true and I is false D. Both statements are false E. Cannot determine § I: a 16. Determine the rate-law expression for the reaction belowoat the temperature at which the ' tabulated initial rate data were obtained. Rate = A l 91 CC 7’ V A + 2B + 3C -) products . 3 Initial B Initial Initial rate los (53‘ 1 0.10 M 0.20 M 0.10 M 4.0 X10-2 “;figgm 0.40 M 0.20M 0.10 M 4.0 x lo-2 . I _ .I 0.20 M 0.20 M 0.20 M 1.6 x 10'1 35° -- @ 0.20 M 0.50 M 0.10 M 1.0 x 10-1 ‘ '. klAllBl EM e = if? as" = \ r 6 lelicr ' , L Q?“ ,l% C.k[C]2 ., . (p 5 16¢ 3-H:th I‘ xi D. k[B]2[C] - S 1.0 HO” @none of the above or cannot determine @ [<0 is h0§M\;m ti (1016 CHEM 128 (Maxwell) Exam 11 October 30, 2003 page 5 17. The data in the table are for the reaction shown below at 6600 K. I A + B + C 9 products 1 1.25mM 1.25mM 1.25mM 6.7 {70 e 1-7—9 a 9:: 2 3.75 mM 1.25 mM 1.25 mM 60.3 371 (-3 100.75 3 1.25mM 1.25mM 3% 49.0 3353*: “UN W2— 4 1.25 mM 3.75 mM 3.38 mM 147.0 " 154%: 2 :51 5 3:31 mM 2.2? mM 111de '2 13%? $133 it, L _l’_ L- [cj __ me; of! 5. fl ' LIT [.3501 (61?. iffy” A. In the space below each of the reactants in the equation, write the apparent order of that M filo-13 reactant in this reaction. (3 points) wt ‘* L“ 35%” B. Write the rate equation for the reaction. (3 points) 34 r 1 Ma -— JR [A3202] {C31 C. Use the data to determine the probable rate for Trial 5 (4 points) Show work or Ioglc for full or partial credit. N7 7 (0b a gfi 3 IQL ’20.; 2'10 . \“F' rJtU-Q‘éjitan 9] E3363?” mg: may 30011019045); ping ; 52.7 ham/$.60 18. Consider the reaction H2 (g) + 12 (g) 9 2 HI (g) Kc = 3.14 X 10'5 at a specified temperature What is the equilibrium concentration of HI (g) when a mixture of 1.200 mol of H; (g) and 0.800 m0112 (g) are allowed to come to equilibrium in a 4.00 liter container at this temperature? (8 points) Show work or logic for full or partial credit. Note, if you feel you need you need to use the quadratic equation to solve this problem, you only need to proceed to the point where you determine your a, b, and c terms. You do not need to actually solve the quadratic equation during the exam time. PM: {We 5 2w“? 1.7.00 @139 t 3‘ 5...?” CHEM 128 (Maxwell) Exam 11 October 30, 2003 page 6 19. On the curve below, determine the apparent rate with correct units at time = 40 seconds. “ ' r (4 points) 6 H Time (sec) 20. 0.800 mole NH; (g) was placed into a rigid 1.00 liter container and the reaction shown below was allowed to come to equilibrium at a particular pressure and temperature. The equilibrium concentration of N; (g) was 0.050 M. 3m“: 2 NH3 (3) S 3 H2 (g) + N; (3)» (SN (4% . . . I . .r i :2, -. A. What IS the value for Kc for this reaction? (8 pomts) J I .‘ _ ‘ - Show work or logic for filll or partial credit. “ a '. 950)] 05 6] - ’lNl‘iufi) r’ QHIUP fNu’p Kg. I c(Boo o , 0 32x ' 43% ll 7 $00 r 254 BX 050 QM \ ' \ J \W’“>‘;3N\~ '(/ *‘ to“ . What is the K1, for this reaction? (4 points) Note, if you were n_ot able to prepare an answer to part A above, let K,3 =12, and proceed from there on this part. he -— rem)” la: CHEM 128 (Maxwell) Exam 11 October 30, 2003 page 7 .y. . -’A particular prepared food has a bacterial contamination. The toxic products of the bacteria i ’ are not detectable for 96 hours if the food is kept the refrigerator at 4.0000. The overall activation energy for the production of the toxic product is 71.1 kJ/mol. This food was taken to a picnic on a hot day with the temperature at 310°C. Given this data, determine (if possible) the number of hours until the toxic product would be detectable at 37 Doc. (8 points) ‘ . ' E Show work or 10 ic for full or partialocredit. a 7 WWNM 64:7“ iw T= two c teem TL= m a 4H: _ . //.:/—/ v JIM/k1. ~7I'W/N‘ .L—i. 011;sz EQNXID'Ew/lwol 3‘0 177 I M 22. The equilibrium constant is shown for the reaction below 2 so2 (g) + 02 (g) r. 2303 (g) Kc = 2.5X104 at 400°C ‘ Determine the value of Kc for the following reactions at the same temperature. (3 points each) A. so2 (g) +1/202 (g): 803 (g) 'L ‘21 /0 (25mm) :ggxlbxmtl‘c B. 4 so3 (g): 4 502(g) + 202 (g) n‘ This page intentionally blank 30 H H < H Ho ofiubmafi H “EEG Amway one USN amaze 8 Eubno mauflom 2.. _.N E. 60mm :3 a m2 r saw u HEM > 88.0 C ASE mEEEWB quEoo 2 $5838 28 comma?“ “8.52 05 95 h 98 E .x mo 83? 8592 muuaumosm c p. —N a a m .., u 3. , . O m . “539% L33 Hmfiozv 3322“ :8 33328 ofi wquflsofiu mén > $86 a Gena “a H M m2 .8 wow H :8 v :3 g M > 83.0 cm “GHQ mafifimoH 5568 8 mushy/ecu an 5.3 :0?an HE h 23 E E mo 33?» 8523 wasfiumnnm .wém as: =8 ‘ M E m H om “GHQ 33:8 -om :8 Eavnfim ufi Sou.“ “Samson Engage 05 3:33 5. FN .. : .Ilmwhkklsfl 1 . .. “$5 Haggai :8 2355 Rt Sod owzmau 3.65 8a @3283 2: Maggi e. 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B an. 5< un— na an MD mm mm wm mm mm mh mm mh .vn mm mm 32 32 33 Sam «New 5% $3 3% 0X u... @5— £2 .5 a: 3 S S cm _ mu _ we _ 5 3 3 3 2. S 8 mm mm R. 8.3 8.3 mm? 3.: ES 2.8 8.8 mm? 8.3 8mm 3mm ES 8% 3.8. was 8-3 8.3 2.8 ..nammaaann-aaanmu mm mm .vm mm mm Fm om mm mm 5N mm .um mm mm Fm ON mp 33 3mm 5% 5.8 8.8 8.8 E. 2 GW m w n w m e m 5.3.. 3% m n. a _< mm mTJialmmimn mm mm mw mm as. «2 9. E. 3. m_. NF E. 9.8 8.2 8.2 5.3 8.2 SE N55 :3 ..aaun .. or m w h m m .v m mood m8; 9 m_. 3 m“. c0230: 9&2 N 83 9N... M. 46 (m <¢ <m mamm: :mo_EE< E250 (N a... 9. C. w «5 4K . manage—m one no 035,! Stomach S CI-[EMIZS (Maxwell) Fall 2003 Blue Sheet for Exam II l- 1‘ , , \"l \‘IM’I '. y . 220112, f, _, 5’ "5“) 12 points, your Oct. 30 exam will be worth 88 points. Bl - - ' WM. Blank “Blue Sheets” will be available at the exam. This me during office hours, etc, or most any time my door is open. If we can hale All Blue Sheets orrectl fill utb 2PM ct 4‘ - u o' - an an - - " ‘ '- completed by that time. All extra credit sheets will h veto be graded at myoce to get my special stamp. Part I. Kinetics. Phosgene is a toxic gas prepared by the reaction of carbon monoxide and chlorine (as it exists in nature). . \OD _ \ ' 3 7, 7r. L0 ' 3 D f” “ —-—-—-—"‘—‘?[Jt C0 (2) + C12 (3) 9 C002 (5) ‘1 WM MO The following date were obtained in a kinetic study of its formation: , f r—= O I jInitial [CO] Initial [C12] Initial Rate | q q x I 5"”) Trial (moi/L) (mol/L) (moi/L's) L 1 I i "5 O 1 1.00 0.100 1.29 X1049 - \ (7,; )(\D 2 0.100 0.100 1.33 X 10’30 3 0.100 1.00 1.29x10-29 10 e "1.) 4 0.100 0.0100 1.32 x 10-3‘ 1 \ \./ Rate law for the formation of phosgene is 5 C0 Cl (2 points) Calculate the average value of the rate constant I . Z l X l 0'15 (2 points) 2. Using the data inliigure 16.10 of your text, make a clearly original plot of In k vs. III‘ that ‘ includes the value for the slope of the line, and the apparent value for the Activation Energy for the reaction. Computer generated plots are welcome, and actually encouraged to build fly your ability to graph in Excel or similar programs, but must include your name as part of , \g/ tithe legend of the graph. However, if you do turn in a computer generated plot, be sure you ) MOO \‘gwp can do this on an exam. Include units with your answer. (4 points) I A , 2,4 {2 (52.71 ’61”) Ar ( EA, ’ W- . . Ea: $.97 £10 J ,cs‘voo - 6—3“, i/mw_ )l 3.47 “3.3? Part 11. Equilibrium (“WWW W N‘ ‘" 0W“ P” \0 \< b“) "wig—g ; £300 1. Hydrogen and carbon dioxide react according to the reaction ' 0 00 l) H2(g)+ 002(g) '9 HiO(g)+ C0(g) A sealed 4.00 liter container, initially holds 0.400 mol of H2 gas and 3.600 mol of CO2 gas. Given that at your particular temperature and pressure, the Ku, = 0.150, determine the equilibrium concentration of CO (g) at equilibrium. Note, your instructor behaves that you will need to use the quadratic equation to solve this problem. (4 points) 3. a; ‘ p [co] = w M (3 sig. fig. minimum) ...
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chem128 ExamII Sum03 - CHEM 128 (Maxwell) Exam II October...

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