105bf07_sample_e4

105bf07_sample_e4 - Chemistry 105bL First Letter of PLEASE...

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Unformatted text preview: Chemistry 105bL First Letter of PLEASE PRINT YOUR NAME IN BLOCK LETTERS 11:00 am. Section Last Name Fall 2005 Name; EXAM #4 November 22, 2005 Last 3 Digits SID #; Professor Arieh Warshel Lab T.A.'s Name: Lab Day and Time: Please Sign Below: I certify that I have observed all the rules of Academic Integrity while taking this examination. INSTRUCTIONS: 1. There are 5 problems on 9 pages in this exam. Please check to see that you have a complete exam. 2. Please show all of your work to receive full credit. 3. You must use ink. Do not use a pencil. Answers written in pencil are not eligibel for regrades. Useful Physical Constants and Equations: Avogadro's number N = 6.022 x 10” mol" Universal gas constant R = 0.08206 L atm K" mol'I = 8.314 J K'1 mol'l Faraday's constant F = 96,485 C mol'l KP=KCCRT)A” k3=§ In k = fig) + lnA Ifax2+bx+c=0thenx=£—:-:i‘£- PV=nRT -W=q§ AS=kB In W AG=~nF§ AG=AG° +RTan AG=AH —TAS E=q+w AG°=—RT1nK,q E=hu=mc2 AG__§fl —T — T+AS Additional Information 8=€°-%1an <) e = 6° — —-—°‘°§” long 0.0592 0 = fl 108W Ken. 8 AGOd) = -96.5 n 8 (volt) fiagijfalcgei tofls) Cu+2 + 2c‘ -¥ Cu(s) Zn“2 + 26‘ -) Zn(s) Ni” + 2c" —-) Ni(s) Mg"2 + 2c‘ -) Mg(s) Cd’z + 26‘ —-> Cd(s) Sn+2 + 2c‘ —+ Sn(s) 73 70 75 76 77 1'. W la 0- Ir mun Ill.“ mam In.” man mm 8° volts_ — 0 14.. M W 0.34 -0.76 —0.23 4.03 -0.40 -O.14 u H and 7| PI ‘7 M mm 6' ? o9 Ir ) 1-- MYJ. 1mm. '00 v 10: ‘ 7- ‘ u. . .0.» 1020 Appendix C / Thermodynamic Quantities for Selected Substances at 298.15 K (ZS'C) AH; 46; 5' AH; 40; s' Subskmce (kl/moi) (kl/mo!) O/mol-K) . Substance 0t] /mol) (kl/mo!) Q/mol - k I cobalt . Magnesium (20(8) 439 393 179 Mm) 147.1 112.5 148.6 Co(s) 0 o 28.4 MB“) 0 0 32.51 M3020) -641.6 ~59z1 89.6 Com, M30(s) -601.8 -569.6 26.8 01(3) 338.4 298.6 1663 M8(0H)z(s) —924.7 —833.7 63.24 01(5) 0 0 3330 CuCl,(s) - 205.9 - 161.7 108.1 Manganese CuO(s) — 156.1 — 1283 42.59 Mn(g) 280.7 238.5 173.6 Cu,0(s) - 170.7 —147.9 92.36 Mn(s) 0 0 32.0 Mn0(s) -3852 —362.9 59.7 Fluorine Mn02(5) - 519.6 - 464.8 53 .1 4 7(3) 80.0 61.9 158.7 Mn0.'(aq) -541.4 -447.2 1912 F'(aq) —332.6 -278.8 -13.8 Fng) 0 0 202.7 Mercury 1mg) - 268.61 —270.70 173.51 143(3) 60.83 31.76 174.89 Hg“) 0 0 77.40 Hydrogen 1-13c1,(s) -730.1 -184.0 1445 11(3) 217.94 203.26 114.60 143,020) —264.9 —2105 1925 14*(44) o o o H+(3) 1536.2 1517.0 108.9 Nickel 112(8) 0 0 130.58 N1(3) 429.7 384.5 182.1 Ni(s) o o 29.9 Iodine Nicus) -3053 -259.0 97.65 1(3) 106.60 70.16 180.66 N100) —739.7 —211.7 37.99 I'(aq) -55.19 —51 57 111.3 12(3) 6225 19 37 260.57 Nimgen 12(5) 0 0 116.73 N(g) 472.7 455.5 1533 111(3) 25.94 1 30 206.3 N2(8) o 0 191.50 NH,(aq) -8029 -2650 1113 Iron NH,(3) —46.19 — 16.66 1925 Fe(g) 4155 369.8 180.5 NH.‘(aq) - 132.5 -7931 113.4 Fe(s) o 0 27.15 Fe"(aq) — 87.86 -84.93 113.4 N,H.(3) 95.40 159.4 238.5 Fe"(aq) — 47.69 - 10.54 2933 NH.CN(s) 0.0 _ _ FeC1,(s) -341.8 —3023 117.9 NH4Cl(s) —314.4 -203.0 94.6 NH.N0,(:) —365.6 — 184.0 151 FeCl,(s) - 400 -334 1423 110(3) 9037 86.71 210.62 860(5) — 271.9 -7552 60.75 Fe,0,(s) -822.16 -740.98 89.96 NOng) 33.84 51.84 240.45 Fe,0.(s) - 1117.1 — 1014.2 146.4 1920(3) 81.6 103.59 220.0 Fe5,(s) — 1715 —160.1 5292 14,043) 9.66 98.28 3043 Nocug) 52.6 663 264 Lead 11141030117) —206.6 — 110.5 146 111(5) 0 0 68.85 HNOg(g) —1343 -73.94 266.4 PbBr,(s) - 277.4 - 260.7 161 Pbco,(s) -699.1 -625.5 131.0 Oxygen Pb(NO;),(aq) — 421.3 -246.9 303.3 0(3) 247.5 230.1 161.0 Pb(NOJ)z(s) — 451.9 — — 02(3) 0 0 205.0 PbO(s) — :173 — 187.9 68.70 o,(3) 142.3 163.4 237.6 OH'(aq) —230.0 - 157.3 — 10.7 Lithium 1110(3) —241.82 —22857 188.83 L113) 159.3 126.6 138.8 H100) -285.83 —737.13 69.91 11(5) 0 0 29.09 H1020) —136.1o — 105.48 232.9 Limaq) — 278.5 - 273.4 12.2 H1010) - 187.8 — 120.4 109.6 11*(3) 685.7 648.5 133.0 LiCl(s) — 408.3 —384.0 59.30 1. (20 points) (i) Using the data on the information page, indicate which is the anode in a cell based on the half cells of: Zn(s) ——> zn+1(1M) + 2e- --0. 74 mad. M p; a “I? Ni(s) —> Ni*2(1M)+Ze‘ “0,23 S'o Mfg/‘5 also determine the potential (8°) for this cell. F os’hhy‘ ' . . Jr " (O No ——> No ++z¢ «0.13 \._, 0 +0 , 5'3 V = 5 “a G) Welc= m‘éfim = M, —-> NJ” +2e’ “ Sivan/M Jaw/Maw (11) Based on the data on the information page, find the equilibrium constant at a for the reaction A Zn(s) + Cd+2 (aq) :‘ Zn+2 (aq) + Cd(s) 2n —> an”+.u' + 0,75 golfing; A doc fiasco @ +0. 34 = 5 ° AG'=—/HF£O= ’RTAk M: 2 Moo—e .v. 4%, W: I t m F8 ° F @ juk= R7. R=?3/¢J-M’ ‘1 7' = 2 78K A k :29.” ' é k 19.0 r-\ = l/ e 2, K : / «TX/0 2. (20 points) (i) Please draw the electric cell formed by using 0.0001 M CdSO4 solution and a Cd(s) electrode and 0.2 M ZnSO4 and a Zn(s) electrode. Determine what is the anode and what (ii) Write down the anode and cathode reactions. 0 t 05:72 Amt: Eds) aa‘nze‘ £3": ‘47" / "a Ea.” a, 24- —— - .. ‘ Mama +2. 601/5) «‘42.- 0.72? =>m+£¢ (iii) Indicate the direction of electron flow in the wire. a”; / @ W En 91¢ 49 CA S’I‘o‘l— 3;”: +0.73 K g at“, .2" -—3 Q6 "'” 52' \v’ +0 . a2 6 V = (v) What concentration of Cd+2 will allow you to change the direction of thg current in the cell? Z .254 52‘”: 0’74.“ 0 ' 1.1- .. #9 gen—40:8aa—Mf’z Lil Cal ‘ " t Z”? 5 J h 4-0. 3 5 , [/0 1/ o . o -0'36= __ $72 (0.2!:- 2. [642+] [Cd “:7: (- W16” A1 6 3. (20 points) (a) Circle "True" or "False" for each of the following. (i) Cathode protection helps to keep a constant temperature in buffers. True (ii) F2 is a good reducing agent. True (iii) Biological systems use electrostatic processes to perform their work. False (iv) When AG0 for an electric cell is zero, the emf must be zero. Tm,“ (b) Draw a battery and write the corresponding chemical reaction. W: Zn —> 2.. ’+ +2¢ - MW: “7””?!- ‘f’QMnflz. +a7e‘—>Mlyo} Pi: Hun, wt 1; 2M1, HI, 0 (c) The potential of an electric cell is 2.00 V. LW hat is the maximum amount of work that can be performed by the cell? 05] AL (a WIWS 4 hamsér m0 2. e/(t'l‘rnvs . M}ka :— ’ $— 2M4): g "M Fgwx [J— Wmnx -" V mé' ((3.5? (3.“ Wmax " ’ 3961';— 7 4. (20 points) How many grams of Ni will be deposited on a metal plate using electrolysis with 1 Ampere current for 3000 seconds? lmfv :/ Goa/Ml? sec IM 8')! “We ll/I/~ 94,78-(0 grade- 0) x a. (S x3aaosx (ii) Will the coverage of an iron plate by Sn prevent corrosion? Explain and quantify your result using the corresponding redox potentials. i.€./ W;// Sn r‘quCE 3+4D F; 7 I Sn ‘9 3’12“ +le— +04? Fezfiac‘ —e E: —0‘W/ «a So 1/: (it! 2? 52.4 Mun‘ é: ftsffi‘ve 9,, if 4. WM, M (sap/,2: 45474142. 5. (20 points) (i) (a) What are the electronic configurations on Fe and Fe”? Fe [AV] 4311:!" o 3%6 e' GS, Fifi [ArJ-y‘ [#2:]: or”; %‘%J, (b) Explain why the oxidation potential (M —-) M+2 + 2e') of Mn is larger than that of Cr. (You must consider the corresponding change in electronic configuration.) Mn EAT] 481%: "9 540'] 34/51}. anf @ Cr [M7 #3456 [kw/"M Cr” l) p4,,“ [5 W4 3% 7‘44”; Crai’ (y: (’5' 2) c?" M #2 M75141 (SWV’ 14" (ii) Circle "True" or "False" for the following: (a) EDTA is a polydentate ligand. False @ (b) The d orbitals are being filled in the transition metal series. @ False (c) The lead battery is used in standard calculat 01's . True (d) Electrolysis can be used to produce 1-11 from water. @ False ...
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This note was uploaded on 07/13/2008 for the course CHEM 105BL taught by Professor Warshel during the Fall '07 term at USC.

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105bf07_sample_e4 - Chemistry 105bL First Letter of PLEASE...

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