PROF. JOHN VERKADE SPRING 2005 THIS EXAM CONSISTS OF 12 QUESTIONS ON 9 PAGES CHEM 167 HOUR EXAM IV APRIL 20, 2005 SEAT NO. NAME RECIT. INSTR. RECIT. SECT. GRADING PAGE Page 2 Page 3 Page 4 Page 5 Page 6 Page 7 TOTAL POINTS 17 pts 21 pts 20 pts 18 pts 16 pts 8 pts 100 pts SCORE NOTE: SHOW ALL OF YOUR WORK ON THESE EXAM PAGES. PUT YOUR ANSWERS IN THE ANSWER SPACES. THE LAST PAGE CONTAINS A PERIODIC TABLE AND USEFUL INFORMATION. THIS SHOULD BE REMOVED AND USED FOR REFERENCE AND SCRATCH PAPER. DO NOT PUT ANSWERS ON THIS TEAR AWAY PAGE. Calculators are not required and they are not to be used. They are to be out of sight. For problems asking for calculations, just set up the problem but DO NOT solve for the answer. PLEASE NOTE that in setting up the problem, you do not need to isolate the unknown. All electronic devices (e.g., calculators, cell phones) and papers (except your test) are to be out of sight. All books, book bags, jackets, caps, hats, etc. are to be UNDER your seat. Please refrain from conversation from now until you leave and are outside the door. Thank you! The Staff appreciates your cooperation. Teaching Assistants and Recitation Sections Name Chunxia Jiang Steven Raders Sections 2, 3 1, 4 Time 10:00, 12:10 9:00, 2:10 End-of-Semester Evaluation Begins Friday, April 22, at 12:00 p.m. End-of-Semester evaluations for the lecturer, recitation and laboratory teaching assistant will be available on WebCT from noon Friday, April 22 until noon Friday, April 29. The evaluations will be available to you based on your recitation or laboratory enrollment. Each student will be able to complete and submit one evaluation for the lecturer, recitation and laboratory teaching assistant. All student responses are anonymous. To complete the evaluation, log-on to WebCT and go to the recitation course you are enrolled in. You will find an End-of-Semester Evaluation link on the homepage that will take you to the evaluation. CHEM 167 FINAL EXAM MONDAY, MAY 2 9:45 11:45 A.M. 1352 GILMAN HALL
1. (12 pts) Consider the following reaction at 1600 C: 2 Br 2 (g) 2 Br(g) When 1.05 moles of Br 2 are put in a 0.980 L flask, 1.20 percent of the Br 2 undergoes dissociation. Calculate the equilibrium constant K c for the reaction. 2. (5 pts) The following equilibrium constants have been determined for hydrosulfuric acid at 25 C: H 2 S(aq) H + (aq) + HS (aq) K c = 9.5 10 8 HS (aq) H + (aq) + S 2 (aq) K c = 1.0 10 19 Calculate the equilibrium constant for the following reaction at the same temperature: H 2 S(aq) 2 H + (aq) + S 2 (aq)
3 3. (7 pts) In the uncatalyzed reaction N 2 O 4 (g) 2 NO 2 (g) the pressure of the gases at equilibrium are P N2 O 4 = 0.377 atm and P NO2 = 1.56 am at 100 C. What would happen to these pressures if a catalyst were added to the mixture? 4. (10 pts) Consider the following equilibrium reaction in a closed container: CaCO 3 (s) CaO(s) + CO 2 (g) This reaction is endothermic in the forward direction. What will happen to the equilibrium if a) the volume is increased? b) some CaO is added to the mixture? c) some CaCO 3 is removed? d) some CO 2 is added to the mixture? e) temperature is increased? 5. (4 pts) Write the formulas of the conjugate bases of the following acids: a) HNO 2 b) HCOOH (formic acid)
6. (10 pts) How much NaOH (in grams) is needed to prepare 546 ml of solution with a ph of 10.00? 4 7. (10 pts) A 0.0560 g quantity of acetic acid is dissolved in enough water to make 50.0 ml of solution. Calculate the concentrations of H +, CH 3 COO, and CH 3 COOH at equilibrium. (K a for acetic acid = 1.8 10 5.)
8. (10 pts) The ph of a 0.30 M solution of a weak base is 10.66. What is the K b of the base? 5 9. (8 pts) The highly reactive OH radical (a species with an unpaired electron) is believed to be involved in some atmospheric processes. Table the bond energy for the oxygen-to-hydrogen bond in OH is 460 kj/mol. What is the longest wavelength (in m) of radiation that can bring about the reaction for an OH molecule? OH(g) O(g) + H(g)
10. (8 pt) Balance the following redox equation by the ion-electron method. 6 Bi(OH) 3 + SnO 2 2 SnO 3 2 + Bi (in basic solution) 11. (8 pts) Calculate the standard emf of a voltaic cell that uses the Mg/Mg 2+ and Cu/Cu 2+ half-cell reactions at 25 C. Write the equation for the cell reaction that occurs under standard-state conditions. o o ( E Mg = 2.37 V, E 2+ / Mg Cu = +0.15 V) 2+ / Cu
12. (8 pts) What is the emf of a voltaic cell consisting of a Pb 2+ /Pb half-cell and a Pt/H + /H 2 half-cell if [Pb 2+ ] = 0.10 M, [H + ] = 0.050 M, and P H2 = 1.0 atm? o ( E Pb +2 / Pb = 0.13 V) 7
8 Periodic Table of the Elements 103 Lr (260) 102 No (259) 101 Md (258) 100 Fm (257) 99 Es (252) 98 Cf (251) 97 Bk (247) 96 Cm (247) 95 Am (243) 94 Pu (244) 93 Np (237) 92 U 238 91 Pa 231 90 Th 232 71 Lu 175 70 Yb 173 69 Tm 169 68 Er 167 67 Ho 165 66 Dy 162 65 Tb 159 64 Gd 157 63 Eu 152 62 Sm 150 61 Pm (145) 60 Nd 144 59 Pr 141 58 Ce 140 8A 18 7A 17 6A 16 5A 15 4A 14 3A 13 Lanthanides Actinides 109 Une (266) 108 Uno (265) 107 Uns (262) 106 Unh (263) 105 Ha (262) 104 Rf (261) 89 Ac 227 88 Ra 226 87 Fr (223) 83 Bi 209 82 Pb 207 81 Tl 204 80 Hg 201 79 Au 197 78 Pt 195 77 Ir 192 76 Os 190 75 Re 186 74 W 184 73 Ta 181 72 Hf 178 57 La 139 56 Ba 137 55 Cs 133 51 Sb 122 50 Sn 119 49 In 115 48 Cd 112 47 Ag 108 46 Pd 106 45 Rh 103 44 Ru 101 43 Tc (98) 42 Mo 95.9 41 Nb 92.9 40 Zr 91.2 39 Y 88.9 38 Sr 87.6 37 Rb 85.5 86 Rn (222) 85 At (210) 84 Po (209) 52 Te 128 53 I 127 54 Xe 131 36 Kr 83.8 35 Br 79.9 34 Se 79.0 33 As 74.9 32 Ge 72.6 31 Ga 69.7 30 Zn 65.4 29 Cu 63.5 28 Ni 58.7 27 Co 58.9 26 Fe 55.8 25 Mn 54.9 24 Cr 52.0 23 V 50.9 22 Ti 47.9 21 Sc 45.0 20 Ca 40.1 19 K 39.1 18 Ar 39.9 17 Cl 35.4 16 S 32.1 15 P 31.0 14 Si 28.1 13 Al 27.0 2 He 4.00 10 Ne 20.2 9 F 19.0 8 O 16.0 7 N 14.0 6 C 12.0 5 B 10.8 8B 2B 12 1B 11 10 9 8 7B 7 6B 6 5B 5 4B 4 3B 3 12 Mg 24.3 11 Na 23.0 4 Be 9.01 3 Li 6.94 2A 2 1A 1 1 H 1.01
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