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2009 Aug - UNIVERSITY OF TORONTO FACULTY OF ART AND SCIENCE...

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Unformatted text preview: UNIVERSITY OF TORONTO FACULTY OF ART AND SCIENCE August Examinations 2009 CHM139H18 Duration — 3 Hours Instructions: Please wait until you have been told that you may begin the test before turning the page. You have 3 hours to complete the 30 multiple choice questions and 3 short answer problems. Electronic calculators may be used. Programs for calculators may not be used. Calculators may not be shared. A periodic table and some data are attached at the back of the test. No other aids are allowed. WHEN YOU RECEIVE YOUR TEST PAPER AND COMPUTER ANSWER SHEET: 1. Write your name, student number and lab demo group number on this page. 2. Write your name and lab demo group number in the box provided on the front of the computer answer sheet. 3. Write your student number in the student ID number field. Write the student number in the first nine columns only. Leave the last column blank. 4. Blacken the circles in the student ID number field which correspond to your student number. Blacken only nine circles. FOR THE MULTIPLE CHOICE SECTION: For each multiple choice question, choose from the available options the response that best answers the posed question. Completely fill in the corresponding oval on your answer sheet with #2 pencil. Your answers are to be recorded on the computer answer sheet and on this paper, both of which must be handed in at the end of the test. Nothing written on the test paper. for the multiple choice section will be marked. The computer answer sheet MUST be filled in DURING the time allotted for the test. FOR THE SHORT ANSWER SECTION: Write your answers in ink in the provided space on the exam paper. AT THE END OF THE TEST: Insert your computer answer sheet into your test paper. Remain seated until all the test papers have been collected. Name: Student No: Lab Demo Group: Student No Part A: Multiple Choice Questions (1 point each) 1. The Keq value for the following reaction is 0.21 at 100 °C: N204(g) 2N02(g) If the partial pressure of N02 is 1.2 atm and the partial pressure of N204 is 0.90 atm at 100 °C, which of the following statements is TRUE? a .The net reaction proceeds towards products. b. The reaction is at equilibrium. c. As the reaction proceeds towards equilibrium, the partial pressure of N02 will increase. d. Q < Keq. e. None of the above. 2. Silver chloride has a solubility of 0.0070 mg/mL in water at 5 °C. What is the osmotic pressure of a saturated solution of AgCl? a. 1.1x10'3 atm b. 0.16 atm c. 2.0 x 10‘5 atm d. 4.9 x 10‘5 atm e. 3.2 atm 3. Ultraviolet radiation has a wavelength of 10‘7 m. Infrared radiation has a wavelength of 10'5m. Which of the following statements is TRUE? a. The intensity of ultraviolet radiation is greater than that of infrared radiation. b. The energy of the infrared radiation is greater than that of the ultraviolet radiation. 0. The frequency of the ultraviolet radiation is greater than that of the infrared radiation. (1. Both types of electromagnetic radiation have the same energy per photon. e. None of the above. 4. For which of the following reactions or changes does entropy INCREASE? N2(g) + 3H2(g) —> 2NH3(g) Cooling nitrogen gas from 20 °C to —20 °C. HCl(g) + NH3(g) ——> NH4Cl(s) CaCO3(s) —> Ca0(s) + C02(g) Compressing a container of a gas from 2.0 L to 1.0 L. 953-9975” 5. The K5,, ofCan is 3.9 x 10'” at 25 °C. What is the solubility ofCan? 2.1 x10'4 M 9.8x 10'12 M 6.2 x10'6M 3.4x 10'4M 3.9x 10'” M {DP-.057!” Page 2 of 1 1 CHM139HIS — Final Exam Summer 2009 Student No 6) A 1.000 kg sample of nitroglycerine, C3H5N309, explodes and releases gases with a temperature of 1985°C at 1.000 atm. What is the volume of gas produced? 4C3H5N309(l) —> 12C02(g)+10H20(g)+ 6N2(g) + 02(g) a. 816.4 L b.1632.2L c. 3878 L d. 5203 L e. 5919 L 7. The aquation of tris(1,10-phenanthroline)iron(II) in acid solution takes place according to the equation: Fe(phen)32+ + 3 H3O++ 3 H20 —» Fe(H20)52+ + 3 phenH+. If the activation ener , Ea, is 126 kJ/mol and the rate constant at 30°C is 9.8x10'3 min", what is the rate constant at 50 C? a. 2.3 x103 min" b. 4.4 x10'4 min'1 0. 2.2 x10" min‘l d. 4.6x100 min'1 e. 9.8x10'3 min'1 8. Which of the following are redox reactions: i) C0(g) + H20(g) 9 0020;) +Hz(g) ii) COz(g) + 2H20(g) —> H3O+(aq) + HCO3'(aq) iii) 2CuS(s) + 02 —> 2Cu(s) + S02(g) iv) 2AgN03(aq) + NaZSO4(aq) 9 2NaNO3(aq) + Ag2S04(s) a. all of the above b. i) ii) and iv) c. iv only (1. none of the above e. i) and iii) 9. Phosphine (PH3) decomposes into phosphorous and molecular hydrogen: 4PH3(g) '9 P4(g) + 6H2(g) Experiments show this reaction is first order with a rate constant of 1.7x10‘2 5'1 at 650 0C. Which of the following statements are TRUE? (i) The overall reaction is elementary (ii) The data allow Ea to be calculated (iii) The rate constant will be smaller than 1.7 x 10'2 s" at 500 °C (iv) The reaction PH3 9 PH2 + H might be the first rate determining step in the mechanism of this reaction a. i, ii, iii and iv b. ii, iii and iv e. iii and iv (1. iv e. iii Page 3 of 11 CHM139H1S — Final Exam Summer 2009 Student No 10. The vapor pressure of liquid chloroform, CHC13, is 400.0 torr at 24.1 °C and 100.0 torr at - 6.3 °C. What is AHvap of chloroform? a. 15.3 kJ/mol b. 30.1 kJ/mol c.45.2 kJ/mol d. 53.6 kJ/mol e. 86.7 kJ/mol 11. Consider the combustion of ethylene: C2H4(g) + 302(g) —-) 2C02(g) + 2H20(g) If the concentration of C2H4(g) is decreasing at a rate of 0.18 M/s, what is the rate of change in the concentration of CO2(g)? a. 0.18 M/s b. 0.36 M/s c. 0.090 M/s d. 0.060 M/s e. 0.54 M/s 12. The half-life for the first order decomposition of H2O2(aq) is 949.5 5. 1f the initial concentration of H202 is 0.850 M, how long will it take for the concentration to reach 0.540M? a. 621.5 s b. 747.3 s c. 925.2 s d. 4.778 x 10“ s e. 545.1 s 13. What is the oxidation state of nitrogen in N02? a. +4 b. +3 c. —3 d. +5 e. +1 14. The following reaction shows all of the reactants and products, but it is not balanced: N0; + Al + OH— + H2O —’ Al(OH)4- + NH3 When it is balanced, one of the terms is a. 2 N02- b. 3 Al c. 2 OH” d. 5 H2O e. 3 NH; Page 4 of 11 CHM139H1S — Final Exam Summer 2009 Student No 15. The reaction of N02 with CO to give C02 and NO can proceed through different mechanisms. What rate law would be consistent for the following rate? determining step? 2 N02 —>N0 + N03 a. Rate = 2k[N02] b. Rate = k[NOz]2 0. Rate = m0” NOgl 2[NOz] d. Rate =|NOHN031 [N02]2 6. Rate = l/2k[N02] 16. For the process of dissolving a solid in a liquid, which of the following statements is true? a. AHSOIn is always negative and A8501n is usually positive. b. AHso]n is always positive and Assam is usually negative. c. AHsoln is either positive or negative and A8501n is usually positive. d. AHsom is either positive or negative and A8501n is usually negative. e. AHsom usually negative and A8501“ is either positive or negative. 17. What is the [OH'] of a solution whose pH is 7.41 at 25 0C? a. 6.59 M b. 2.57 x 10'7M c. 3.89 x 10'8M d. 6.59 x 10'14M e. 7.41 M 18. What is the role of the electrolyte in a galvanic cell? a. To facilitate rapid diffusion of the redox reagents to each other b. To facilitate electron transport though the solution c. To complete the electrical circuit by ion transport d. To increase the cell voltage e. None of these 19. Which one of the following decreases as the strength of the attractive intermolecular forces increases? a. the heat of vaporization. b. the normal boiling point. e. the extent of deviations from the ideal gas law. d. the sublimation temperature of the substance. e. the vapor pressure of liquid. Page 5 of 11 CHM139HIS — Final Exam Summer 2009 Student No 20. At a given temperature the vapor pressures of benzene and toluene are 183 mm Hg and 59.2 mm Hg, respectively. Calculate the mole fraction of benzene in the vapor phase over a solution of benzene and toluene with Xbenzene = 0.600. a. 0.600 b. 0.678 c. 0.756 d. 0.823 c. 0.901 21. Hydrogen peroxide decomposes to water and oxygen according to the reaction below: 2 H2O2(aq) "’ 2 H20(l) + 02(g) In the presence of large excesses of 1' ion, the following set of data is obtained. What is the average rate of disappearance of H2O2(aq) in M/s in the first 45.0 seconds of the reaction if 1.00 L of H202 reacts at 25°C and 1.00 atm pressure? Time, s 02 (g) Collected, mL 0.0 0.0 45.0 2.00 90.0 4.00 135.0 6.00 a. 9.09 x 10‘7 M/s b. 1.64 x 10'4 M/s c. 4.33 x10'5 M/s d. 3.63 x 10'6 Ms C. 6.21 x 10'3M/s 22. The decomposition of hydrogen peroxide is given by the following reaction: 2 H202(aq) "’ 2 H200) + 02(g) In the presence of K1 the reaction is thought to occur by the following mechanism: Step 1: H202 + I' -' H2O + 10' Step 2: 10' + H202 -* H2O + 02 +1" What is the role of I' in this mechanism? a. frequency factor b. catalyst c. transition state d. intermediate e. spectator Page 6 of 11 CHM139HIS —— Final Exam Summer 2009 Student No 23. A refrigerator uses a compressor to do work to “remove hea ” from warm items placed in it. A foam cup containing 150 g of water at 23.0 °C is placed in a refrigerator. What is the minimum work the compressor must do to cool the water to 1.5 °C? a. 180 k] b. 13 kJ c. 3.2 kJ d. 770 J e. 36 k] 24. What is the standard free energy change for the following redox reaction at 25°C? (Ag+/Ag: 13": 0.8 V; Curr/Cu: 13°: 0.3 V.) 2 Ag+(aq) + Cu (3) —> 2 Ag (5) + Cu2+(aq) a. 50 k] b. -50 kJ c. 100 kJ d. —-100 k] e. 150 k] 25. A 55.0 mL sample of0.15 M HCl is added to 45.0 mL of0.20 M NaOH. What is the [H+] of the resulting solution? a. 8.3 x 10‘3M b. 2.2 x WM 0. 1.4 x 10"2M d. 2.8 x10"12 M e. 6.4 x 10‘13M 26. The decomposition of ammonia to nitrogen and hydrogen on a tungsten filament at 800°C is independent of the concentration of ammonia at high pressures of ammonia. What is the order of the reaction with respect to ammonia? a. zero b. first c. second d. third e. not enough information Page 7 of 11 CHM139HIS — Final Exam Summer 2009 Student No 27.. Aluminum is used in a battery in which the following reaction occurs: 4 Al (5) + 3 02 (g) + 4 OH‘ (aq) + 6 H20 -->4 Al(OH) 4‘ (aq) If the battery must supply a current of 78 A for 4.0 hours, what mass of Al (in g) must be contained in the battery? a. 110 g b. 180 g c. 430 g d. 316 g e. not enough information to answer 28. When equal molar amounts of the following sets of compounds are mixed in water, which will not form a buffer solution? a. NaH2P04 with NazHPO4 b. NH3 with NH4Cl c. CH3C02H with NaCH3C02 d. HNO3 with NaNO3 e. HF with NaF 29. Which one of the following statements about the solid-liquid-vapor phase diagram shown below is FALSE? l vapour D Pressure (atm) Temperature (K) a. Point B represents a melting point for the substance. b. C represents the triple point. e. The liquid phase boils at point D. d. K represents the normal boiling point for this substance. e. There are different phases present at point B than at point M. Page 8 of 11 CHM139HIS — Final Exam Summer 2009 Student No 30. At which concentration of H+( AGOf = 0 kJ/mol) and CH3COO‘ (AGOf = —372.5 kJ/mol) will the dissociation of 1 M acetic acid, below, become spontaneous? (AGof for CH3C02H(aq) = —399.6 kJ/mol) CH3C02H (aq) —> H*(aq) + CH3CO2' (aq) a. 11 M b. 0.99 M c. 4 x 10‘3M d.2x10"5M e. 1x10‘8 M Part B: Short answer Questions. 1. The following reaction is not spontaneous under standard conditions as written, having a cell potential of -1.104 Volts: 8 points ' 2Ag(s) + Zn2+(aq) + 20H' —> Ag20(s) + Zn(s) + H200) Zn2+ + 2e' —’ Zn E° = —0.76 V. a. Calculate the standard reduction potential for the half-reaction Ag20(s) + H20(l) + 2e' —> 2Ag(s) + 20H'(aq). b. Calculate AG° for the reaction as written. Page 9 of 11 CHM139HlS - Final Exam Summer 2009 Student No c. Rewrite the redox reaction so that it will proceed spontaneously. Which half-reaction reaction will occur at the anode? 2. An important reaction in the formation of photochemical smog is the reaction between ozone and NO: NO+O3->N02+02 The reaction is first order in NO and 03. The rate constant of the reaction is 80 M l s'1 at 25°C and 3000 M 1 s'1 at 75°C. 8 points a. Does the reaction happen in one step or multiple steps? b. What is the value of activation energy of the reaction? c. What is the rate of the reaction at 25°C when [N0] = 3 x 10'6M and [03] = 5 X 10'9M Page 10 of 11 CHM139H1 S — Final Exam Summer 2009 Student No d. Predict the values of the rate constant at 10°C and 35°C. 3. Single-use "hand warmers" sold at ski areas are based on the rapid, exothermic reaction of finely divided iron with oxygen: 4 points 4 Fe (s) + 3 02 (g) —> 2 Fe203 (3) AH = -l644.32 k] a. How much heat is produced from 55.85 g of iron? b. How many grams of iron are required to produce 500 kJ of heat? Page 11 of 11 CHM139HIS — Final Exam Summer 2009 Equations E = hv c = Av A = h/mv AxAmv 2 M47: _ —1s 2 2 E__2-_18_xl£’..l n:1,2,3,,_, Ema n:1,2,3,... V=R.c.[iz-iz n 8mL m n 1/2 PV=nRT P +V —— f—(V nb): nRT Em = éRT u“ = (fl) 2 g MM P 1‘on 1 + P2 + P 3 +. . . P A XAP (at P solution = Xsolventp solvent ATb = K bcm AT, = —Kfcm H=MRT AHWP 1 1 q=nCAT w=-PAV AE=q+w AH=AE+A(PV) lnP2=lnP1+ R F—T 1 2 S=Nklna2 AS=—;I: Mm: AS+AS AG: AH TAS AG: AG +RTan surr AG” =~RTaneq AH“ = Z coefi'p - AH;.(pdts) — Z coeff, . AH} (rots) AS“ = Z coeflp -AS} (pdts) — Zcoefl, -AS} (rcts) AG“ = Z coeffp -AG; (pdts) — Z caeff, -AG; (rots) E = E” — Elf—ZnQ Ecell = Em»: — Eun I= nC /t G°= -nFE° n E [A] ]=_k 1 1 lnk = 1n “ _. .__.__ = RT ln[[A]——o [Al [AL A— = c A" H: K 1 l—1 Ky K (RT p p a + othAJ pH = —log[H+] pOH = - loglOH-7 pH + pOH = 14 K“ 'Kb = Kw —bi-\/b2 —4ac V=4/3 m3 P0rax2+bx +c=0, x= 2 a Atomic mass unit Avogadro’s number Boltzmann’s constant Faraday’s constant Fundamental unit charge Gas constant Heat capacity of water Planck’s constant Rydberg’s constant Speed of light Zero point Kw of H20 at 25°C Physical and Chemical Constants 1 a.m.u. = 1.6605402 x 10'27 kg NA = 6.0221367 x 1023 mole'1 k = 1.380658 x10'23 J K" F = 9.6485309 x 104 0 mole'1 e =1.60217733 x10"19 c R = 8.314510 J mole" K'1 = 0.082058 L atm mole'l K" C = 4.184 J g'1 K" = 75.4 J mol'1 K'1 h = 6.6260755 x 10'34 J 5 RH = 2.1798 x10'18 J = 1.097 x 10-2 mm-1 c = 2.99792458 x 108 m s" 0°C = 273.15 K Kw=1.00x 10'l4 Conversion Factors 1 atmosphere (atm) = 1.01325 x 105 Pa (N m'z) = 760.0 mm Hg (torr) = 1.01325 bar 1 calorie (cal) = 4.184 joules (J) 1 debye (D) = 3.335617 x10'3o c m 1 eV/paxticle = 96.485 kJ mole" = 23.061 kcal mole'l 1 eV = 1.602 x 10'19 J = 8067 cm" 1 kcal mole" = 4.184 kJ mole" = 349.73 cm'1 1 kJ mole" = 0.23901 kcal mole" = 83.591 cm‘l 1L atm = 101.325 J = 24.217 cal In x = 2.3026 log x 7: = 3.1415927 Eou.é§[email protected]>_u£ engm> $3 5:3 h .3335 m_ 220$ 350$ cm 3.2.: .5. van .coEmonEoo cisofi 3.53:3 uzmtflomfigu a gas on WD_Z_._.U< 3 can in. it 3:25.» suam «25 .2326: .EwEmfi 05 E 323. vo>__..mom:o_ 9.: yo 52:5: 35: m5 3.59 3935.5 :_ vane—us» w:_m> m5 .3 0.23m 9: gm... meEoE Eu. .mflamu Emu Em 0 9... 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