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2011 Aug - UNIVERSITY OF TORONTO £4 FACULTY OF ARTS AND...

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Unformatted text preview: UNIVERSITY OF TORONTO £4 FACULTY OF ARTS AND SCIENCE W919 AUGUST EXAMINATIONS 2011 $959 CHM139H1 SUMMER Name (print): Student No: Demonstration Gp. No.1 DURATION: 3 HOURS TOTAL MARKS = 64 Calculators may be used but not shared. Programmable calculators may not be used. A PERIODIC TABLE and USEFUL DATA are attached to the back of the exam. WHEN YOU RECEIVE YOUR EXAM PAPER AND COMPUTER ANSWER SHEET: 1. Write your name, student number and demonstrator group number on this page. 2. Write your last name and initials in the box provided at the top right of the computer answer sheet. Blacken the appropriate circles for your last name and initials. 3. Write your student number along the top of the student number box and blacken the circles which correspond to your student number. 4. In the box titled FORM, fill in the circle marked ’A’. YOUR ANSWERS ARE TO BE RECORDED ON THE COMPUTER ANSWER SHEET AND ON THIS PAPER BOTH OF WHICH MUST BE HANDED lN AT THE END OF THE EXAM. AT THE END OF THE EXAM: Insert your computer answer sheet into your exam paper. Remain seated until all exam papers have been collected. QUESTION (PART B) mun-10 TOTAL (PART A) = [30 EXAM TOTAL = [64 PART A: MULTIPLE CHOICE QUESTIONS (1 mark each): 1. 42.6 g Cu are combined with 84.0 g of HNO3 according to the reaction: 3 Cu + 8 HNO3 —> 3 Cu(NO3)2 + 2 N0 + 4 H20. Which reagent is limiting and how many grams of Cu(N03)2 are produced? A) Cu, 93.8 g B) HNO3, 93.8 g C) Cu, 125.6 g D) HNO3, 125.6 g E) Cu(NO3)2, 125.6 g 2. Niels Bohr promoted the connection between the periodic table and quantum theory. Which of the following statements is INCORRECT? A) The link between the periodic table of elements and quantum theory is electron configuration. B) Elements in the same group have similar electron configurations. C) Elements in the same group have the same number of electrons in the outermost shell. D) Elements in the same group have the same principle quantum number. E) Elements in the same group have the same number of valence electrons. 3. 53.5 g of an ideal gas of molecular weight = 30.5 g/mol is confined at a pressure of 133 mmHg. The density of the gas is 0.228 g/L. Calculate the temperature of the gas. A) 261°C B) me C) -57°c D) 285°C E) 42°C 4. If a liter of C02 is compared to a liter of H2, both at 25°C and one atmosphere pressure, then: A) the C02 and H2 molecules have the same average speed B) there are more H2 molecules than CO2 molecules C) the average kinetic energy of the CO2 molecules is greater than that of the H2 molecules D) the C02 molecules are, on the average, moving more slowly than the H2 molecules E) the mass of one liter of CO2 equals the mass of one liter of H2 5. The volume correction term in the van der Waals equation is present because: A) barometers are inaccurate B) molecules are diatomic C) molecules attract each other D) molecules occupy volume E) molecules repel each other 6. What is the volume, occupied by a mixture of 16.0 g Ne(g) and 42.0 g Ar(g) at 15.0 atm pressure and 25°C? A) 94.6 L B) 3.01 L C) 1.71 L D) 1.29 L E) 0.252 L 7. Which of the intermolecular forces is the most important contributor to the high surface tension shown by water? A) dipole-dipole forces B) dispersion forces C) hydrogen bonding D) ion-dipole forces B) surface tension is not a result of intermolecular forces. 8. The enthalpy of vaporization at 298 K for diethylether (C4H100) is 26.0 kJ/mol. How much heat would be required to vaporize 1.00 L of the ether at 298 K if its density is 0.714 g/L? A) 4401 B) 250J C) 186J D) 1301 E) 74.11 9. Arrange the following compounds in order of increasing boiling point: I) l-propanol, CH3 CH2CH20H; II) 1,2-propanediol, CH3CH(OH)CH20H; III) 1,2,3-propanetriol, (glycerol), HOCH2CH(OH)CH20H. A) 11,111, I mme C) 111, I, 11 D) III, 11, 1 E) 1, III, 11 10. A solution containing 3.24 g of sulfur in 40 g of benzene boils 0.81°C above the boiling point of pure benzene. Determine the number of S atoms in one molecule of dissolved sulfur. Kb for benzene is 253°C m-l. A) 10 B) 12 C)6 D) 8 E)4 11. Which of the following has no effect on the rate of a reaction? A) the value of NJ" for the reaction B) the activation energy of the reaction C) presence of a catalyst D) the temperature of the reactants E) the concentrations of the reactants 12. For the reaction: 2N205(g) -+ 4N02(g) + 02(g) the rate law is: A[021 = N k[N2051 _ At 300 K, the half-life of the reaction is 2.50 x 104 seconds and its activation energy is 103.3 kJ/mol. What is the rate constant at 310 K? A) 2.78 x 10-5 s-1 B) 7.29 x 10-6 s-1 C) 7.29 x 10—8 s-1 D) 3.70 x 10-5 s-1 E)1.05 x 10-4 s-1 13. What is the activation energy for the destruction of ozone? Use the data shown on the graph. A) 14 U B) 392 kJ C) 406 U D) -14 kJ E ) the graph does not provide Reaction Prague: enough information to answer this question. 14. For the second-order reaction A —> products, the following data are obtained: [A] = 3.024 M, t: 0 min [A] = 2.935 M, t= 1.0 min [A] = 2.852 M, t= 2.0 min What is the concentration of [A] after 4 min? A) 2.70 M B) 2.58 M C) 0.76 M D) 1.76 M E) 2.42 M 15. Consider the following reaction. C(S) + H20(g) =‘- CO(g) + H209.) At equilibrium at a certain temperature, [HzO(g)] = 0.12 M, and [CO(g)] = [Hz(g)] = 1.2 M. If all of these concentrations are suddenly increased by 0.50 M, which of the following statements is true? A) the concentration of the products will increase. B) Kc = 4.66 C) the concentration of H20(g) will increase. D) since Kc does not change, nothing happens. E) Kc has to be multiplied by 0.5. 16. For the reaction: CH4(g) + 2 H20(g) =‘- C02(g) + 4 H2(g); AH" = +190 kJ, what happens when catalyst is added to the system: A) the reaction equilibrium shifts to the right B) the reaction equilibrium shifts to the left C) the AH" increases D) the temperature increases E) there is no change in the equilibrium, catalyst changes reaction rate only 17. For the exothermic reaction: 3 Fe(s) + 4 H20(g) == Fe304(s) + 4 H2(g), when the temperature of the system is increased, which of the following statements is correct? A) the reaction equilibrium shifts to the right. B) there is no change in the reaction equilibrium. C) the reaction equilibrium shifts to the lefi. D) the Kp of the reaction is independent of temperature. E) the Kc of the reaction is independent of temperature. 18. A saturated aqueous solution of calcium hydroxide has. a pH of 12.25. What is the [Ca2+] of such a solution? A) 0.018 B) 5.6 x 10-13 C) 2.3 x 10-5 D) 0.035 E) 8.9 x 10-3 19. A solution of an unknown acid had a pH of 3.70. Titration of a 25.0 mL aliquot of the acid solution required 21.7 mL of 0.104 M sodium hydroxide for complete reaction. Assuming that the acid is monoprotic, what is its ionization constant? A) 9.0 x 10-2 B) 2.0 x 10-4 C) 4.4 x 10-7 D) 3.6 x 10-9 E) 2.7 x 10—11 20. What is the molar solubility of PbI2 (Ksp = 7.1 X 10'9) in 0.10 M Pb(NO3)2? A) 1.3 x10~4M B)2.6 x10-3 M C)7.1><10-8M D) 2.7 x10-4M E)2.7 ><10-5M 21. In the unbalanced equation shown below how many moles of electrons are transferred per mole of reducing agent? C2042- (£161) + Mn04‘(aq) —> C02(aq) + Mn2+(aq) A) 1 B) 2 C) 3 D) 5 E) 10 22. Which of the following processes would result in a decrease in system entropy? A) melting of an ice cube B) sublimation of a moth ball C) evaporation of a puddle of gasoline D) a glass of cool lemonade warming in the sun E) condensation of water vapor on a cold windshield 23. In a sealed container, the rate of dissolving is equal to the rate of crystallization. Therefore we would expect: A)AG<0 B) AG>0 C) AG=0 D)AS=O E)AH=0 24. The signs of AG, AH, and AS at 25°C are shown below for three reactions. reaction AG AH AS I. - + + 11. — - + 111. - - - Which reaction could go in the reverse direction at high temperature? A) 1 B) H C) 111 D) I and II E) 1 and 111 25. Gold does not react with either nitric acid or hydrochloric acid but does react with a combination of both called aqua regia. Identify the oxidizing agent in the following equation: Au(s) + 4 H+ + NO3- + 4 C1- ——> [AuC]4]- + 2 H20 + N0(g) A) Au B) H+ C) N03- D) Cl- E) NO3- and H+ 26. A salt bridge is used to A) provide reactants in a fuel cell. B) determine the direction of the cell reaction. C) control whether the cell is electrolytic or galvanic. D) allow the ion flow necessary for cell neutrality. E) provide a transport for the electrons. 27. In a galvanic cell, the half-reaction MnO4-(aq) + 8 H+(aq) + 5 e- ——> Mn2+(aq) + 4 H200) is A) an oxidation half-reaction and occurs at the anode. B) an oxidation half-reaction and occurs at the cathode. C) a reduction half-reaction and occurs at the anode. D) a reduction half—reaction and occurs at the cathode. E) the overall reaction 28. Consider the following table of standard half-cell potentials: A2+2e--—>2A- E°=+1.09V B4++2e-—+B2+ °=+0.15V C3++3e-——+C °=-1.66V D2++2e-—~)D °=—2.37V M++e— ~>M °=—2.77V Which substance is the strongest oxidizing agent? A) A2 B) 134+ C) (33+ D) D2+ E) M+ 29. For a dead battery A) E is negative and AG is positive for the cell reaction. B) E is negative and AG is negative for the cell reaction. C) E is zero and AG is positive for the cell reaction. D) E is zero and AG is zero for the cell reaction. E) E is zero and AG is negative for the cell reaction. 30. How many grams of nickel metal are plated out when a constant current of 15.0 A is passed through aqueous NiC12 for 80.0 minutes? A) 14.7 g B) 21.9 g C) 43.8 g D) 48.4 g E) 56.1 g PART B. SHORT ANSWER QUESTIONS: Answers must be written in pen in the boxes provided. Be sure to show all steps of your work. 1. (10 marks) Fluoroacetic acid occurs in the South Africa gifblaar, one of the most poisonous plants in the world. The pKa of fluoroacetic acid (CHzFCOOH) is 3.59. (a) Calculate the pH and the percent dissociation in a 0.10 M solutiOn of fluoroacetic acid. (b) If 1L of 0. 1 0 M solution of CHZFCOOH is titrated with 300 mL of 0.20 M NaOH, what is the final pH of that solution? (c) In one experiment, a 40 mL solution of 0.10 M CHzFCOOH is titrated with 0.100 M NaOH. In a separate experiment 40 mL of a 0.10 M hydrochloric acid (HCl) solution is titrated also with 0.100 M NaOH. On the graph below sketch the two titration curves. ‘4 l 2 10 pH 6 4 2 0 0 20.0 40.0 60.0 80.0 mL of 0.1 00 M NaOH added 9 m 2. (16 marks) In 1909 Fritz Haber established the conditions under which nitrogen, N2(g), and hydrogen, H2(g), would combine to form gaseous NH3 : 3H2 (g)+ N2 (g) ‘9 2NH3(8) The yield of ammonia is approximately 10-20%, and the process takes place at ~ 500 °C, at very high pressure (~250 atmospheres), and requires a metal catalyst. The following information is available at standard conditions: AH° kJ/mol AS° J/mol-K (a) Calculate AH ° at 25 °C for this reaction: (b) Calculate AS° at 25 °C for this reaction: (c) Is the reaction spontaneous at standard conditions (25 °C)? Prove your statement by calculating the appropriate criterion. (d) Calculate the temperature at which this reaction will be at equilibrium: 10 (e) Why, do you think, catalyst is needed for this reaction? Explain briefly. (t) Calculate the equilibrium constants Kp and K for the reaction at 500 °C (g) The NH3 is produced at high pressure. Explain briefly the effect of high pressure on the position of this reaction equilibrium. 3.(8 marks) Consider the galvanic cell depicted below. Assume standard temperature and pressure. 11 (a) Write the balanced reaction equation and shorthand cell expression for this cell. (b) What is AG° for this reaction? (c) What is the equilibrium constant for this reaction? (d) What is Ecell if the ions that participate in the reaction at the cathode are present at 10 M concentration, and ions that participate in the reaction at the anode are present at 0.001 M? 12 PHYSICAL AND CHEMICAL CONSTANTS Atomic mass unit 1 a.m.u. = 1.6605402 x 10'27 kg Mass of an electron me = 9.109 x 10'31 kg Mass of a neutron mn = 1.674 x 10‘27 kg Mass of a proton mp = 1.672 x 10'27 kg Avogadro’s number NA = 6.0221367 x 1023 mole"1 Boltzmann’s constant k5 = 1.380658 x 10431 I<'1 Faraday’s constant F = 9.6485309 x 104C mole"1 Fundamental unit charge 6 = 1.60217733 x 10'19C Gas constant R = 8.314510] moIe'1 K1 = 0.082058 L atm mole'1 I<'1 Heat capacity of water S = 4.184.! g"1 K1 = 75.4] mole“1 K'1 Planck’s constant h = 6.6260755 x 10341 5 Rydberg’s constant R... = 2.1798 x 1018] = 1.097 x 10'2 nrn'1 Speed of light c = 299792458 x 108m s'1 Zero point 0°C = 273.15 K Kw of H20 at 25°C Kw = 1.00 x 10'14 Pl T! = 3.1415927 CONVERSION FACTORS 2.54 cm = 1 inch 1 N = 1 kg m s"2 1 kg = 2.205 pounds (lbs) 1 nm = 10'9 m 1 A = 10*" m 1 Watt = 1 Joule sec'1 1 Amp = 1 C/s 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 x 103° c m 1 eV/partlcle = 96.485 kJ mole'1 = 23.061 kcal mole'1 1 eV = 1.602 x 10491 = 8067 cm" 1 kcal mole‘1 = 4.184 U mole‘1= 349.73 cm'1 1 k] mole“1 = 0.23901 kcal mole‘1= 83.591 cm'1 1 L atm = 101.3251= 24.217 cal USEFUL EQUATIONS E=hv A=c/v A=hlmv Ephomn=hvo + Ek 5.. = - RHZZInZ PV=nRT (P+n2a/V2)(V-nb)=nRT KE = V; mu2=3RT/(2NA) urms = (3RT/M)”2 4Tb = Kbm ATf = Kim H=M RT Psolution=xsolventPsolvent ax2 + bx + c = 0 X =‘_M=_2‘/§E—__43€ In(ab) = In(a) + In(b) ; In(a/b) = -ln(b/a) KP=KC(RT)A"; An = c + d - (a +b) Arrhenius equation: k = Ae'Ea/RT pn[:_2]=(i l_i] x R T: T1 First order reaction: |n{[A]o/[A]} = kt Second order reaction: 1/[A] — 1/[A]o = kt Zero order reaction: [A]: -kt + [A10 pH = -log[H30*] pOH = -|og[OH'] pH + pOH = 14 Kax Kb = Kw q=nCAT W=—PAV AE=q+w AH=AE+PAV $=kan A$=% Asuniv=A$+A$surr AH ° = Z coefprH; (pdts) — Z coeffiAH;a (rcts) A$° = Z coefips ° (pd ts) — Z coeffrs° (rcts) AG" = Z coefipAG‘,’ (pdts) — Z coefifiAG; (rcts) AG = AH — TAS AG =AG° + RTan AG° = -RTan RT C E=E°—-——Ina =2. __ "F I t AG.— nFE PERIODIC TABLE OF THE ELEMENTS . 8 http:/Avwmluf-.rplit.brlperiodn0’en/ 2 4.0026 g 1 00000110010003 00002111043005 He "‘ m‘c’m(°’19‘“gs,'m'm‘“‘<" m/ ‘c‘L‘m((s,§$‘°1m“°E 13 IIA 14 NA 15 VA 16 VIA 17 VIIA Ham 13 111A 5 10.011 6 12.011 ’1 14.007 8 15.999 9 10.990 10 20.100 mm 1 mmvznomc MASS 1 2 Be 5 1““ " B C N 0 F Ne unuuu 5M“ B ' 000011 CARBON NITROGEN OXYGEN Hymns NEON 11 22.990 12 24.005 0000 WNAME 13 20.002 14 20000 15 30.914 16 02005 17 35.153 18 09.040 Na g m ' A1 Si P 5 Cl Ar SODIUM 14091158qu 3 013 4 NB 5 VB 6 VIB ‘7 VIIB 8 9 10 11 I3 12 “B ALUMINIUM moon 1 knows swam OHLORINE ARGON 19 39.090 20 40.070 2144.050 22 47.007 2350.042 24 51.000 25 54.030 26 55.015 27 50030 28 50.003 29 63.540 30 05.39 31 09.723 32 7204 33 74.022 34 70.90 35 70.904 36 00.00 Ca Sc Ti V Cr Mn Fe CO Ni Cu Zn Ga Ge As Se Br ‘ Kr CALCIUM W 'ITMIUN VANADIUM CHRONIUM mums: 1am COBALT NICKEL COPPER mo GALIJUH WM ARSENIC SEBIUM BROMNE KRYFTON 38 07.02 39 00.900 40 91.224 41 02.900 42 9094 43 (90) 44 101.07 45 10201 46100.42 47107.07 48 11241 49 114.02 50 110.71 51 121.70 52 127.00 53 120.00 54 1:11.29 Sr Y Zr Nb MO Tc Ru Rh Pd 'Ag Cd In Sn Sb Te I Xe FUJBIDIUM STRONTMM YI'TRIUM INCONIUM NIOBKJM “WWW" RUI'HENIW RHODW PNJADMM StLVER CADMIUM 011310111 TIN ANTIMONY TEUJRHJM IODINE W 55 13201 56 137.33 57.71 72170.40 73 100.05 74 103.04 75 186.21 76 190.23 77 192.22 78105.00 79 100.97 80 200.59 81 204.30 82 2072 83 200.00 84 (200) 85 (210) 86 (222) Cs Ba Ida-L“ Hf Ta W Os Ir Pt Au Hg Tl Pb Bi PO At Rn CAESIUM BARNM ' '- HAFNIUM ‘mN'rALUM TUNGSTEI RHEIIUM OSMUM IRIDIUM cow MEROURV THAUJUM LEAD BISMUTH POLONIUM ASTAYINE RADON 87 (223) 88 (226) 89-103 104 (201) 106 (200) 107 (204) 108 (277) 109 (200) 110 (201) 111 (272) 114 (209) 7 F Ra - RE D90 Sg BBB H0 M0 Ema FRANGIUM RADIUM Mb- DlBNIUM SEABORGIUM BOHRQUM HASSIUM MWUM UNUNNILIJM UNUNUNIUM - ~ 1 “‘ . . 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