Sp07Exam2wAnswers

Sp07Exam2wAnswers - Name Section TA Test 66 Chemistry 116~C...

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Unformatted text preview: Name Section TA Test 66 Chemistry 116~C EXAM II Total Points m 150 Monday, 6:30 PM March 5, 2007 THIS EXAM IS FOR STUDENTS WITH MONDAY—WEDNESDAY 10:30 LECTURE. YOU SHOULD HAVE AN ORANGE COMPUTER ANSWER SHEET! Directions: Each student is responsible for following directions. Read this page carefully. Write your name and other requested information on this page and on the separate answer Sheet. CODE your name on the answer sheet using an ordinary (#2) pencil. CODE your correct lot—digit identification number (PUID) on the answer sheet. THIS IS VERY IMPORTANT! CODE your section number on the answersheet. Please use all fo_ur digits, 0101, 0102, 0201, etc. This is also very important! CODE the test number shown in the upper right~hand corner on the answer sheet in the block labeled “Test/Quiz Number”. This is Test 66. Put all calculations on the examination pages. DO NOT PUT ANY EXTRA MARKS ON THE COMPUTER ANSWER SHEET! This exam consists of 20 multiple-choice questions worth 7.5 points each, plus 2 bonus questions worth a total of 6 points. Choose the @ best or correct answer for each question and write it both on your exam paper w on the computer answer sheet. The computer answer sheet is the only one that will be graded! This exam consists of 8 pages plus a Periodic Table, a page of Useful Information and 2 scrap pages. Piease check to be sure that you have them all! END OF EXAM 1) Please make sure that you have entered 22 answers on your scan sheet. 2) Make sure that you have entered your name, ID number, and lab section number (4 digits). 3) You MUST turn the scan sheet in to your TA before leaving the examE Chem li6-C v Exam 2 (Test 66) —- 3/05/07 1. Determine the equilibrium constant for the reaction: (CH3)3BNI"13(g) 4“ N(CH3)3(g) 2‘ (CH3)3BN(CH3)3(E)+ NH3(g) given the following reactions and equilibrium constants (CH3)3BNH3(£§) ‘1' (CH3)3B(g) +NH3(g) K12 0.151 (CH3)3BN(CI~13)3(g) e (CH3)3B(g)+N(Cl-lg)3(g) K2=0.0154 (a) .00233 (b) 0.102 (c) 0.675 (d) 1.48 (e) 9.81 2. At 700 K, the reaction: 2 802(g) + 02(g) v—* 2 803(g) has an equilibrium constant (expressed in terms of concentrations) Kc = 4.3 x 106, and the following concentrations are present: [s02] 2 0.02 M {021: 0.10 M [303} = 20.0 M Is the system at equilibrium? If not, will the system shift toward reactants (left) or toward products (right) to reach equilibrium? (a) not at equilibrium, will shift toward reactants (b) not at equilibrium, will shift toward products (0) yes, the system is at equilibrium ((1) there is not enough information to tell 3. According to Le Chatelier‘s Principle, for the exothermic reaction: 2 H209 + 02(g) ‘1 2Hzolgl increasing the temperature the equilibrium constant, and increasing the volume shifts the equilibrium position to the (a) increases, right (b) increases, left (0) decreases, right (d) decreases, left (e) does not affect, right Chem 116-C —— Exam 2 (Test 66) — 3/05/07 4. Given below is the pH curve for the. titration of a weak monoprotic acid, HA, with the strong base NaOI—l. The approximate value of the pKa for this acid is: (a) 2.5 (b) 4 (c) 5 (d) 8.5 (e) I 3 6 8101214161820 votume of 0.20 M NaOH added (mL) 5. Consider the gas phase reaction: 2 NO(g) + Br2(g) e 2 NOBr(g) When equilibrium is reached at temperature T, the partial pressures are: P(NO) = 0.50 atm P(Br2) = 1.50 atm P(NOBr) 2 6.00 atm What is the value of Kp for this reactiOn at temperature T? (a) 144 (b) 8 (c) 32 (d) 96 (e) 1.0 x 10—2 6. Consider the following reaction: 2 C02(g) e 2 (lots) + Ozts) At a certain temperature, when 2.0 mole of C02 (g) is placed in an Otherwise empty l.0—L container and allowed to come to equilibrium, the concentration of CO(g) is 0.80 M. The equilibrium constant, K, for this reaction at this temperature is: (a) 0.18 (b) 0.43 (e) 1.2 (d) 5.1 (e) none of the above Chem 1 16-C m Exam :2 (Test 66) — 3/05/07 4 Which of the following is the conjugate base of sulfurous acid, H2803? 7. 10. (Q (n (G M) (e also; SO32" Hsog" H330; H2804 Which statement describing chemical equilibrium is FALSE? (3) (b) (C) (d) (6) A system that is disturbed from an equilibrium condition will undergo a net reaction that reduces the effect of the disturbance. Equiiibrium in molecular systems is dynamic, with two opposing processes balancing one another. The value of the equilibrium constant for a given reaction depends on the temperature. In general, the equilibrium constant is large for a rapid reaction and it is small for a slow reaction, . At equilibrium, QC, the reaction quotient, equals K0, the equilibrium constant. The acid dissociation constant Ka equals 1.26 x 1sz for HSO4_ and is 5.6 x 10—10 for NHX. Which statement about the following equilibrium is correct? (a) (b) (C) (d) HSOflaq) + NH3(aq) a soften) + Nartaqi The reactants will be favored because ammonia is a stronger base than the sulfate anion. Neither reactants or products will be favored because all of the species are weak acids or bases. The products will be favored because the hydrogen sulfate ion is a stronger acid than the ammonium ion. The initial concentrations of the hydrogen sulfate ion and ammonia must be known before any prediction can be made. The reaction is impossibie to predict, since the strong acid and the weak base appear on the same side of the equation What is the pH of a 1.0 L solution that contains 47.1g of the weak acid phenol (C6H50H) (molecular weight 2 94.11 g/rnol). Ki: 1.0 x 10'“)? (a) (b) (C) (d) (6) 0.3 5.2 3.8 i0.0 10.3 Chem i 16-C — Exam 2 {Test 66) —— 3/05/07 5 ll. HBrO has pKae%ual to 8.64. The value of Kb for the BrO' is: 3 (a) 2.3 x 10 (b) 4.4 x 10—9 (c) 8.6 x 10“9 (d) 4.4 x 10‘6 (e) 2.3 x 105 12. Which of the foliowing 1.0 M solutions, when combined, will produce a buffer solution? (a) sodium hydroxide (NaOH) and HCl (hydrochloric acid) (b) hydrochloric acid (HCl) and acetic acid (CHaCOOH) (c) acetic acid (CH3COOH) and hydrocyanic acid (HCN) (d) sodium hydroxide (NaOH) and ammonia (Nils) (e) propanoic acid (CH3CH2COOH) and sodium propanoate (CHsCHzCOONa) 13. Which of the following 1M soiutions will be the strongest acid? (a) HOCIO (b) Home2 (c) HOCl03 (d) They Wili all be the same strength (e) There is not enough information give to determine the answer. 14. For the following reaction: CO(g) + 2 H2(g) 4-: CH30H(g) At temperature T, the equilibrium constant for the reaction is 5.0 X 10—3 . A sealed container at temperature T is filled with an initial concentration of 0.50 M CO and 0.50 M H). The concentration of methanol (CI-I3OH) at equilibrium is closest to: (a) 0.50 M (a) 1.3 x 10”3 M (c) 2.2 x 10'3 M (d) 6.3 x 10‘4 M (e) 0.35 M Chem 1 16-C ~ Exam 2 {Test 66) — 3/05/07 6 15. A buffer solution contains 0.50 M HA (pK.1 = 8.00) and 0.25 M NaA. What is the pH after 0.10 mol ofl-ICI is added .to this solution, giving a total final volume of 2.0 L? (a) 1.00 (b) 7.40 (c) 7.56 (d) 7.75 (e) 7.94 16. Which of the following acids should be used to prepare a buffer with a pH of 4.5? (a) canmoon). K. = 2.9 x 10’4 (c) HOC6H4OCOOH, K. a 1.0 x 10'3 (c) engcoon, K. = 1.8 x 10"5 (d) csngo5coon'2, K. = 4.0 x 10‘6 (e) HBrO, K. = 2.3 x 10“9 17. Given three separate solutions containing equal concentrations of formic acid (Ka = 1.7 x 10—4), phenol acid (Ka =' 1.0 x 10%), and acetic acid (Ka m 1.8 x 10”), select the response below that has the acids arranged in order of increasing acid strength: (a) formic < phenol < acetic (b) acetic < formic < phenol (c) phenol < acetic < formic (d) formic < acetic < phenol (e) No response is correct. 18. What is the reaction quotient, Q, for the following chemical reaction? 4 H3O+(aq) + 2 (El—(aq) + Mn02(s) c Mn2+(aq) + 6H.0(t) + 011g) {Ecotr‘ [011211011021 (3) 1M112+11H20161<3121 (b) [Mn2+]{HzO]6{012l [H30+]4 {or ]2 [M11021 (0) 1Mn2+116121 [H30+] [or]2 [H3004 101‘]2 (d) _ ._._ 1Mn+11CI21 (e) None of these expressions is correct. Chem 1 l6~C v Exam 2 {Test 66) - 3/05/07 19. In the following equilibrium reaction, NH3(aq} +1120(E) :2 NH4+(aq) + (DH—(aq) 7 which species are considered bases according to Bronsted-Lowry theory? (a) both NH3 and Nl-Lfr (b) both HZO and NHg (0) both 1120 and OH“ (d) both H20 and Nit.+ (e) both NH3 and OH— 20. What is the pH ofa 0.25M ammonia (NHg) solution? [Kb = 1.76 x 105} (a) 2.68 (b) 4.92 (c) 5.36 (d) 8.63 (e) 11.32 EXTRA CREDIT 21. How many moles of a carbonic acid species (HA) and its conjugate base (A") do you need (4 pts.) to add to 3.0 L of water to make a 0.60 M carbonate buffer at pH 10.00? For carbonic acid (H2C03) pKa1 = 6.37 and pKag = 10.26. ONLY give the number of moles of HA in the answer. (a) 4.2 x 10‘4 moles HA (b) - 0.61 moles HA (c) 1.2 moles HA (d) 1.8 moles HA (e) 0.21 moles HA 22. What were the major safety violations made by the woman scientist in the clips that we (2 pts.) watched in class from the movie “The Andromeda Slrain (a) Drinking out of a beaker in the lab (b) Smoking in the lab (0) Blowing up methane—filied soap bubbles (d) a and b (e) a, b and c Chem 116-C ~— Exam 2 (Test 66) — 3/05/07 Potentialiy Useful Information Constants: R = 0.0821 L—atm/mol~K R a 8.3145 J/mol-K O K = -273.15 °C I aim = 760 torr Formuias: pH = pKa + log ([A-] / {HAD Kp : KC(RT)A“ sea 33 $3.8 ES 33 2 a $6 $3 $8 $8 $8 3mm 2 ms .5 0z 2; E mm 5 gm EU E< .5 m2 2 E m2 m2 :: as 3 M3 3 ea 3 3 mm a a 3.: ob: $2 33 32 32 35 32 32 35 5: 33 3 A; 5:. km on 5 fl. 5 am am E E E 2 am we S 3 3 3 8 S G 8 .. If! . 2.. .‘, QB RE .933 63V @3 sea 28V 93 «2 mm 2Q mm u< N: W: o: 9: WE m2 2: mm a: 89 $2 38 35“ 9.08 0.5 $2 S2 32 . as: Q: a.me . 3: 2 cm a an fl um i E : mo m 3 E. E 3 mu m 3w 3 mm 5 0w 2. E R on Q 3 mm 2 E‘ on a 22 $2 9:: 32 S: we: 3: 32 $2 33 32 $3 3.8 3% mm; 5.3 $3 3.3 x H d. am am 5 5 3 PM . FE am up oz 32 km a hm am a m mm a om 9,“ wv Q 3 Q 3 Q NV 3 3 mm mm 2 km m m m to. m H M 0.68 2H. 00 HIIITJJIII 3 am @335 fl “was V am am a . m m 3% 82 93: SE 6.3. 3% 3.8 3% 3mm 8% 3.2 3% 8.8 3% a». a E 90 «0 cm 5 2 so on :2 6 > w m mm Mm E om am 3. R 8 mm 3% 2 mm 8 am 32 3% E U m a WM 5 o n E . ‘ $3 8.2 8.2 3.3 8.2 $2 oz m o z u m 2 o w h w m 83‘ an N 358on 05 wo oEmH BUB,“ko Spring 2007 CHM 1 16 Exam H Answers Form #66 I) E 2) A 6) A 7) C E l) D 12) E 16) C 17') C Extra Credit 2i)C 22)D 3)]3 8)D 13)C 18)C 4)13 9)C 14)D mg 5) D 10)B :5) c 20) E ...
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Sp07Exam2wAnswers - Name Section TA Test 66 Chemistry 116~C...

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