Test 4 Key - Page 0 Lab Section #— Summerw F0 ;§;i ' The...

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Unformatted text preview: Page 0 Lab Section #— Summerw F0 ;§;i ' The University of Arizona Chem 152 Summer 2009 Andrew I. Grail, PhD EXAM N0. 4 Lab TA Name THE FOLLOWING MUST BE COMPLETELY FILLED-IN OR YOUR EXAM WILL NOT BE GRADED. NAME: PRINT (clearly) THERE IS A 3-POINT PENALTY FOR I LEGIBLE NAMES or improper Scantron information. DIRECTIONS: ODO NOT OPEN THE EXAM UNTIL INSTRUCTED TO DO SO. OYOU MUST USE PENCILS ON THE SCANTRONS OON YOUR SCANTRON m WRITE AND BUBBLE IN YOUR STUDENT ID STARTING ON THE LEFT — FOR THE ‘8’ AT THE BEGINNING, BUBBLE IN A ZERO oON YOUR SCANTRON — WRITE AND BUBBLE {N YOUR LAST AND FIRST NAMES SEPARATED BY A SPACE cFILL IN THE CORRESPONDING FORM LETTER-WA or B OKEEP ALL PAPERS IN FRONT OF YOU, ON YOUR DESK AT ALL TiMES. OFOR MULTIPLE CHOICE QUESTIONS, BUBBLE IN THE LETTER ON YOUR SCANTRON OF THE CHOICE THAT BEST ANSWERS THE QUESTION. UNLESS NOTED THERE IS ONLY ONE CORRECT CHOICE. IF MORE THAN ONE CHOICE IS SELECTED THE QUESTION WILL BE MARKED WRONG. SELECT THE CLOSEST NUMERICAL ANSWERS IF YOUR CALCULATION IS SLIGHTLY DIFFERENT. oPOINT ALLOCATION FOR EACH QUESTION IS INDICATED. OWHEN YOU HAVE FINISHED PUT THE SCANTRON SHEET INSIDE THE BOOKLET BEFORE HANDING IT IN. oHOLD YOUR PICTURE ID UP TO YOUR FACE WHEN TURNING IN AN EXAM My signature below certifies that I have used a calculator for numerical calculations only and that I haw: not done anything unethical while taking this exam. I have read and understand the directions NAME—— SIGN Page 1 Multiple Choice — Choose the BEST answer to each question and bubble it in on the scantron. Each problem is worth 4 points. 1. Iffor a reaction AG : 0, then A) The reaction is at equilibrium B) AHD must be negative C) K = 1 D) K = 0 2. For a reaction that has an equiiibrinm constant of 75000, what must be true? A) AG” is negative D) AH” is positive B) AG“ is positive C) AH“ is negative 3. Use the standard half-eel! potentials listed below to calculate the standard cell potential for the foilowing reaction occurring in an electrochemical celi at 25°C. (The equation is balanced.) 3Clz(g) + 2Fe(s) ——> 6C? (aq) + 2117::3+ (aq) C12(g) + 2e" —> 2Cl—(aq) E° = +1.36 V Fe3+ (aq) + 3e” —>Fe(s) E° = —0.04 V A) +4.16 V B) —1.40 V C) -1.32 V E) +1.40 V D) +1.32 V 4. For a standard voltaic ceEl using the following half-reactions, what must be true? "-0.44 V —0.13 V Fez+(aq) + 2e' -) Fe(s) E0 sz+(aq) + 2e' —> Pb(s) E" II It A) The mass of the iron electrode increases B) Electrons leave the leave the lead electrode to the iron eiectrode C) The concentration of Pb2+(aq) decreases D) The iron electrode is the cathode 5. If the lead-acid storage battery eeli only produces about 2 V according to its standard cell potential, how does a commercial lead-acid battery output 12 V? A) The concentrations of the reactants are adjusted to get 12 V B) The battery is run at very high temperatures C) There are actually 6 cells in series in the battery D) The battery is run at very low temperatures § i i E E i i i E i Page 2 6. If a redox reaction has Etc“ 2 +1.50 V, which of the foilowing statements is true? A) The reaction requires the application of >150 V to go forward B) The reverse reaction is nonspontaneous C) The reaction has a positive AG D) The reaction has an equilibrium constant, K < 1 7. For a battery to work, what must be true of the chemical reaction occurring within it? A) Em]; must be negative C) AG” must be negative B) K < 1 D) The reaction must be exothermic 8. Given the spontaneous reaction, Co(s) + Ni2+(aq) 9 Coz+(aq) + Ni(s), what would increase the voltage of the system? A) Adding more Co(s) B) Decreasing [Ni2+] C) Decreasing [Coh] D) Adding more Ni(s) 9. The oxidation number of nitrogen in Mg(NO3)2 is A) +10 B) —1 C) +1 D) +2 E) +5 10. Which of the following is an oxidation-reduction reaction? A) HC1(aq) + LiOH(aq) —> LiCKaq) + H200) B) NaI(aq) + AgNO3 (aq) ~—> AgI(s) + NaNO3(aq) C) Pb(CZH302)2 (aq) + 2 NaCl(aq) —> PbCI2 (s) + 21‘IaC21-I302 (aq) D) Mg(s)+ 2 HCl(aq) m) MgC12(aq)+I-I2(g) E) All of the above are oxidation-reduction reactions. 11. Given that E? for X + e- 9 Y is greater than 33° for A + 2e- 9* B, it is correct to say that, under standard conditions A) X will oxidize A D) Y will reduce A B) B will oxidize X E) Y will oxidize A C) B will reduce X Pace 3 D 12. For a reaction, if Q<K and the system is spontaneously moving towards equilibrum, A) AG is negative and AG" is negative C) the reaction is at equilibrium D) AG is positive and you can’t teil the sign of AG" E) AG is negative and you can’t tell the Sign of AG” B) AG is positive and AG" is positive 13. In the following reaction, 4H+(aq) + 2V02+(aq) + Ni(s) -> Ni2+(aq) + 2V02+(g) + 2H20(i) rl‘he oxidizing agent is A) H“ B) vog,+ C) Ni D) VO2+ E) H20 14. Baiance the foliowing redox reaction if it occurs in acidic solution. What are the coefficients in front of H"and Fe3+ in the balanced reaction? { m 51% 71! 93;; 3e 3&ng ... ‘9 "" Eff/f“ w. Feflwaq) +Mn04"(aq) —> Fe3+(aq) +Mn2+(aq) + m“? we fix; 9 1a fig {a B) 14*: 8, Fe“: 5 E) 14*: 8, Fe“: 1 A) H+=2, Fe3*=3 C) H+=3, Fe3+=2 D) H*=s, Fe“: 1 15. Which of the following reactions would have the smallest value of K at 298 K? A) A + B -»~> C; E°cen=+L22V B) A + 2B ~—> C; E°cell= +0.98 V C) A + B m) 2C; E°celi = —0.030 V D) A + B we 3C; E°ceu= +0.15 V E) More information is needed to determine. 16. Which of the following reactions would be the most spontaneous at 293 K? M74 <6" W {69/ A) A + 2B —> C; E°cen=+038 V B) A -i- B —) 2C; Eoceil= 3-930 V C) A + B —> 3C; E°cen= +0.15 V D) A + B —> C; E°ceu=+1.22V E) More information is needed to determine. g g ; E x4 g“: 2:?! rwflfia (f g5“ ,ae?§ Page 4 17. At 25 "C, calcuEate the voltage of the cell Cu2+(aq)(0.9033 M) + Mg(s) 9 Mg2+(aq)(2.74 M) + Cu(s) if E°cen = 2.71 V. A) -2.80 V B) 2.62 V C) 2.71 V D) 2.12 V E) —1.94 V 18. How many electrons are transferred in the following reaction? (The reaction is unbaianced.) Mg(s)+A13+(aq) —) A1(s) + Mg2+(aq) A)6 B)2 C)3 D)1 E)4 19. AG Ail reactant All product Extent of reaction According to the above graph, point x indicates that the reaction A) is at equilibrium C) has Q > K B) has K > 1 D) will meeed toward the products J Page 5 20. For the following nonionic amino acid structure, "0 ' HEN c—QH The pKa of the carboxylic acid group is 2.0, and the pKa of the protonated amine is 10.5. What is the dominant structure of the amino acid at a pH of 7.0? .o‘ .a A) '0 B) ‘0‘ .. ll .. .. if -9 HEN C--QH HEN cwg: C) "0" D) "0* a ll -9 G) H .. H3N C-—Q3 H3N C—QH 21. What is the oxidation number of the carbon with the * in the foilowing structure? H .0. I ll .. H-—~»-~C———C* N—H | l H H A) —3 B) +1 C) —1 D) —2 E) +3 22. From the following excerpt from a standard reduction potential table, which substance is the strongest reducing agent? E°V A) Ni2+ B) Ni C) Fe2+ 1)) Fe g: é E E E Page 6 23. From the following table, which substance is the strongest oxidizing agent? E°V A) C102 B) Clo; C) Fe3+ D) Fe2+ 24. The following is one possible structure of the carbonate ion: .. 2- The real structure consists of A) 2 C—0 and 1 C=O B) 3 C=O _ C) 3 C—0 D) three identical bonds partially between a single and a double bond E) three bonds that rapidly change between being single and double bonds 25. The ionic compound, Ca(N03)2, can be classified as A) soluble in water B) insoluble in water C) covalently-bonded D) a good conductor of electricity in its solid form Page 7 Periodic Tabfe 3 1A EZA : 3B 4B 55 g as E 73 33 13 I 23 E3101 E4731 ESA iGA 7A 8A m - .1. - -_1 .-_.WWW....--.....--.21...“--.mmm- . 31 H He 5 3 1008 4.003E WW WA .4 M M w m<————-— u——mu—1.m—-~v.n— n 1—--mumanW»,VWMVVMVVWymwwvwm.wflw.mm WW V.<WWWW4:M»WAWW(“W/01:20“ A qum: <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< «A» 47,».‘(WV ME 31 3 4 5 6 7 ‘8 E9 10 12 1.1 Be _ gB C N 10 'F Ne E 6.941 9.012' _310.81 12.01 14.01}16.00E19.00 20.18 ” 11 E12 13 14 15 16 17 18 :3 Na Mg AI Si P S CI Ar § 22.99 _24.31._ - __ . 26.98 28.09-30.97 320735.45 39.95} i 19 20 21 22 [23 24 $25 26 [27 28 29 ' 30 31 32 33 34 35 [36 34 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge -As Se Br Kr . 39.10 40.08 44.96 418815034 52.00 54.94. 55.85 58.93 58.69 63.55 65.39 69.72 72.61 74.92 789679.90 83.80[ 3 37 38 '39 40 341 42 43- '44 E45 "[46 ' 47 48"” 49 - 50 ' 51 52' 3’53 54 5 Rb Sr Y Zr Nb Mo Tc Ru 'Rh Pd Ag Cd In Sn Sb Te 11 Xe 85.47 87.62 88.91 91.22 92.91 95.94 (98) 101.1 102.9 106.4_107.9 112.4_114.8 118.7 121.8 127631269 131.3 1 55 56 57* 72 73 74 75 ' 76 77 78 79 80 81 82 83 84 85 86 6 CS Ba La Hf Ta W Re 05 If Pt Au Hg TI Pb Bi Po At Rn ! 132.9 137.3 138.9 178.5 180.9 183.9 186.2 190.2 192.2 195.1 197.0 200.6 204.4 207.2 209.0 (209) (210) (222) 120 ( 107 108 109” “ Bh 'Hs Mt (262) (255) (266) 111 269 (272) 87 88 89148104 '105 106 Fr Ra Ac Rf Db $9 (223) 226.0 227.0 (261) (262) (263) Equations: AG 2 AH — TAS AG" = —RTan AG 2 AG0 + RTan E" = (RT/nF)InK AG" 2 mnFE" E a E" —'(RTlnF)an R = 8.3145 J/(mol K) F = 96485 C/mol TK 2 Tag 4- 273.15 1 V = I J/C E“ : (0.0592/n)10gK E = E° — (0.0592/n)logQ RT/F 2 0.0257 WWMmmmmwflmmmm1W6mm11.WWm2wgmwmeww--------------~WWW-mmum1w»wmwwmm1MWMM.W\W2WM.WWW1WWW-mmwummmvmwwAmwwwmwwmnmww68mmwxwgmwwwwn 13W...” ,a 0 (W. ~ ...
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This note was uploaded on 11/23/2009 for the course CHEM 152 taught by Professor Grall during the Summer '08 term at University of Arizona- Tucson.

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Test 4 Key - Page 0 Lab Section #— Summerw F0 ;§;i ' The...

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