Name Section # Chem 102H Final Exam - Spring 2005 PHYSICAL CONSTANTS/CONVERSION FACTORS Speed of light = 3.00! 10 8 m/s Planck s const. = 6.63! 10-34 J s Avagadro s Number = 6.02! 1023 Electron charge = 1.602! 10-19 C Faraday s const. = 96487 C mol -1 (e ) Gas const.(r) = 0.0821 L atm mol-1 K-1 = 62.4 L torr mol-1 K-1 = 8.314 J mol -1 K -1 = 1.987 cal mol-1 K-1 Mass of e = 0.00055 amu = 9.1094! 10-31 kg 0 C = 273 K 1.00 atm = 760 torr 1 inch = 2.54 cm 1.00 lb = 454 g 1 Å = 1.0! 10-8 cm 1 ev = 1.602! 10-19 J 1.0 cal = 4.184 J (exact) Mass of p = 1.0073 amu = 1.6726! 10-27 kg Mass of p = 1.0087 amu = 1.6749! 10-27 kg 1 Scores 1 /7 2 /7 3 /8 4 /10 5 /15 6 /14 7 /10 8 /24 9 /10 10 /25 11 /20 Tot. /150 2.1 1.0 1.0 H Li Na 0.9 0.9 K Rb 0.8 Cs 0.8 1.008 6.941 22.99 39.10 85.47 132.9 Fr (223) 1 3 1.5 11 1.2 19 1.0 37 1.0 55 1.0 87 1.0 Pauling Electronegativity Be 9.012 Mg 24.30 Ca 40.08 Sr 87.62 Ba 137.3 Ra (226) 4 12 20 1.3 38 1.2 56 1.1 88 1.1 Sc 44.96 Y 88.91 Ti Zr La Hf 138.9 V Nb Ta Cr Mo W Mn Tc Re AcUnqUnpUnhUns (227) 21 1.4 39 1.3 57 1.3 89 47.88 91.22 178.5 22 1.5 40 1.5 72 1.4 104 50.94 2.1 92.91 180.9 23 1.6 41 1.6 73 1.5 105 52.00 95.94 183.8 24 1.6 42 1.7 74 1.7 106 54.94 (98) 186.2 25 1.7 43 1.8 75 1.9 107 (261) (262) (263) (262) 2.1 Fe 55.85 Ru 101.1 Os 190.2 H 1.008 1 26 1.7 44 1.8 76 1.9 Co 58.93 Rh 102.9 Ir 192.2 27 45 77 1.8 1.8 Ni Pd 1.8 58.69 106.4 Pt 195.1 Atomic molar mass (Atomic weight) 28 1.8 46 1.6 78 1.9 Cu 63.55 Ag 107.9 Au 197.0 29 1.6 47 1.6 79 1.7 Zn 65.39 Cd 112.4 Hg 200.6 2.0 1.5 30 1.7 48 1.6 80 1.6 B 10.81 Al 26.98 Ga 69.72 In 114.8 Tl 204.4 5 2.5 13 1.8 31 1.9 49 1.8 81 1.7 C 12.01 Si 28.09 Ge 72.61 Sn 118.7 Pb 207.2 6 3.0 14 2.1 32 2.1 50 1.9 82 1.8 N 14.01 P 30.97 As 74.92 Sb 121.8 Bi 209.0 7 3.5 15 2.5 33 2.4 51 2.1 83 1.9 O 16.00 S 32.07 Se 78.96 Te 127.6 Po (209) 8 4.0 16 3.0 34 2.8 52 2.5 84 2.1 F 19.00 Cl 35.45 Br 79.90 I 126.9 At (210) 9 17 35 53 85 He 4.003 Ne 20.18 Ar 39.95 Kr 83.80 Xe 131.3 Rn (222) 2 10 18 36 54 86 Lanthanide series Actinide series 1.1 Ce 1.2 140.1 58 1.1 59 1.1 60 1.1 61 1.1 62 1.1 63 1.1 64 1.1 65 1.1 66 1.1 67 1.1 68 1.1 69 1.0 70 1.2 Pr 140.9 Nd 144.2 Pm (145) Sm 150.4 Eu 152.0 Gd 157.2 Tb Dy Ho Er Tm Yb Lu Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr 232.0 90 1.3 231.0 91 1.5 238.0 92 1.3 (237) 158.9 162.5 93 1.3 94 1.3 95 1.3 96 1.3 97 1.3 98 1.3 99 1.3 100 1.3 101 1.3 102 1.5 (244) (243) (247) (247) (251) 164.9 (252) 167.3 (257) 168.9 (258) 173.0 (259) 175.0 (260) 71 103
2 (1) (7 pts) Would you expect powdered solid aluminum to act as an oxidizing agent or as a reducing agent? (Explain in one sentence.) (2) (7 pts) The specific activity of 14 C in the biosphere is 0.255 Bq g -1. What is the age of a piece of papyrus from an Egyptian tomb if its beta counting rate is 0.153 Bq g -1? The half-life of 14 C is 5730 years. (1 Bq = 1 disintegration s 1 ) (3) (8 pts) Calculate the amount of energy released, in kilojoules per gram of deuterium ( 2 H), for the fusion reaction 2 2 4 1 H + 1H 2 He 2 1 H atomic mass = 2.014101778 u 4 2 He atomic mass = 4.002603250 u
3 (4) (10 pts) Natural lithium consists of 7.42 % 6 Li and 92.58 % 7 Li. Much of the tritium ( 1 3 H) used in experiments in fusion reactions is made by capture of neutrons by 6 Li atoms. (a) (6 pts) Write a balanced nuclear equation for the process. (What is the other particle produced?) (b) (4 pts) After 6 Li is removed from natural lithium, the remained is sold for other purposes. Is the molar mass of the leftover lithium greater or smaller than the natural lithium? (Explain.)
4 (5) (15 pts) Given the following data for the reaction NO 2 (g) + O 3 (g) NO 3 (g) + O 2 (g) Expt. Initial [NO 2 ] Initial [O 3 ] mmol L -1 mmol L -1 Initial Rate mmol L -1 s -1 1 0.21 0.70 6.3 2 0.21 1.42 12.7 3 0.41 0.70 12.4 4 0.66 0.18? (a) (6 pts) Write the correct form of the rate law and give the overall reaction order in the place provided below. rate = d[o 2 ] dt = overall order = (b) (5 pts) Give the value of the rate constant with the correct units. (c) (4 pts) Use the data to predict the reaction rate in experiment 4.
5 (6) (14 pts) Certain bacteria use penicillinase (β-lactamase) to decompose penicillin and render it inactive. The Michaelis-Menten constants for this enzyme and substrate are K M = 3.7 10 5 mol L 1 and k 2 = 2 10 2 s 1. (a) (7 pts) What is the maximum rate of decomposition of penicillin if [penicillinase] = 6 10 7 M? O R HN H S O N COO CH 3 CH 3 penicillin, a β-lactam (b) (7 pts) At what substrate (penicillin) concentration will the rate be half that calculated in part (a)?
6 (7) (10 pts) In our review session, we calculated the equilibrium constant for the disproportionation of In + in aqueous solution from reduction potentials: In 3+ (aq) + 2e! In + (aq) E 0 = "0.40 V In + (aq) + e! In(s) E 0 = "0.21 V 3 In + (aq)! 2 In(s) + In 3+ (aq) K eq = 2.7 # 10 6 Thallium lies below indium in the periodic table. Calculate the equilibrium constant for the analogous reaction for thallium: Tl 3+ (aq) + 2e! Tl + (aq) E 0 = 1.25 V Tl + (aq) + e! Tl(s) E 0 = "0.34 V 3 Tl + (aq)! 2 Tl(s) + Tl 3+ (aq) K eq =?
7 (8) (24 pts) Use the following reduction potentials in answering this question. Pt 2+ (aq) + 2e! Pt(s) E 0 = 1.20 V NO 3 (aq) + 4 H 3 O + + 3e! NO + 6 H 2 O E 0 = 0.96 V PtCl 4 2 (aq) + 2e! Pt(s) + 4 Cl E 0 = 0.73 V (a) (8 pts) From the information given, decide whether Pt will dissolve in hydrochloric acid. Show the reactions that should be considered, then explain why you think the answer is yes or no. (b) (8 pts) From the information given, decide whether Pt will dissolve in nitric acid. Show the reactions that should be considered, then explain why you think the answer is yes or no. (c) (8 pts) From the information given, decide whether Pt will dissolve in aqua regia (a mixture of HCl and HNO 3 ). Show the reactions that should be considered, then explain why you think the answer is yes or no.
8 (9) (10 pts) A galvanic cell is constructed that carries out the reaction: 2 Ag(s) + Cl 2 (g) 2 Ag + (aq) + 2 Cl (aq) If the partial pressure of Cl 2 (g) is 1.00 atm, the initial concentration of Ag + (aq) is 0.25 M, and that of Cl - (aq) is 0.016 M, calculate the initial voltage generated by the cell at 25 C. (10) (25 pts) The galvanic cell Zn(s) Zn 2+ (aq) Ni 2+ (aq) Ni(s) is constructed using a completely immersed zinc electrode that weighs 32.68 g and a nickel electrode immersed in 575 ml of 1.00 M Ni 2+ (aq) solution. A steady current of 0.0715 Amperes is drawn from the cell as it operates. Use information given in the reduction potentials at the end of the exam. (a) (4 pts) Which reactant is the limiting reactant in this cell? (b) (6 pts) How long does it take for the cell to be completely discharged? (c) (7 pts) How much mass has the nickel electrode gained or lost (indicate which) when the cell is completely discharged? (d) (8 pts) What is the concentration of the Ni 2+ (aq) when the cell is completely discharged?
9 (11) (20 pts) Lanthanum(III) phosphate crystallizes as a hemihydrate, LaPO 4 ½H 2 O. When it is heated, it loses water to give anhydrous lanthanum(iii) phosphate: 2(LaPO 4 ½H 2 O(s)) 2 LaPO 4 (s) + H 2 O(g) (a) (3 pts) The magnitude of the entropy change for this reaction is 140.5 J mol 1 K 1. What is the sign of S? positive negative (circle the correct answer) (b) (7 pts) This reaction is thermodynamically spontaneous at 127 C. Compute an estimate for H for this reaction. (c) (10 pts) This reaction is first order in the chemical amount of LaPO 4 ½H 2 O. The rate constant was measured at two different temperatures: Temperature ( C) k (s -1 ) 205 2.3 10-4 260 12.3 10-4 Compute the activation energy of this reaction.
10
11 Acidity and Basicity Constants Acids pk a Bases pk b chloroacetic acid, CH 2 ClCOOH 2.85 aniline, C 6 H 5 NH 2 9.37 hydrofluoric acid, HF 3.46 pyridine, C 5 H 5 N 8.75 acetic acid, CH 3 COOH 4.75 hydroxylamine, NH 2 OH 7.97 hypochlorous acid, HClO 7.53 ammonia, NH 3 4.75 hydrocyanic acid, HCN 9.31 methylamine, CH 3 NH 2 3.44 hydrosulfuric acid, H 2 S 6.89 (pk a1 ) 14.15 (pk a2 ) Solubility Products K sp magnesium hydroxide, Mg(OH) 2 1.1 10-11 magnesium fluoride, MgF 2 6.4 10-9 barium carbonate, BaCO 3 8.1 10-9 mercury(ii) sulfide, HgS 1.6 10-52 copper(i) bromide, CuBr 4.2 10-8 nickel hydroxide, Ni(OH) 2 6.5 10-18 copper(i) iodide, CuI 5.1 10-12 tin(ii) iodide, SnI 2 1.0 10 4 iron(iii) hydroxide, Fe(OH) 3 2.0 10-39 silver bromide, AgBr 7.7 10-13 lithium fluoride, LiF 1.7 10-3 silver chloride, AgCl 1.6 10-10 K sp