CHEM 205 2000FINAL


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Unformatted text preview: GIVEN NAMES): STUDENT NUMBER: THE UNIVERSITY OF BRITISH COLUMBIA FINAL EXAMINATION, APRIL 2000 lecturer. CI- 05 (Physical Chemistry) SIGNATURE: Dr. NE. Burlinson SURNAME: (PRINT. CAPITALS) [2301’ THIS EXAMINATION CONSISTS 0F 11 NUMBERED PAGES . PLEASE CHECK THAT YOU HAVE A COMPLETE EXAMINATION PAPER. Attempt ALL Nine (9) questions. All work must be shown in this booklet. Time: 2.5 Hours USE or anmnmn ' [TLA'I'ORS Is N01 PERM 'D BULBS GOVERNING EXAMINATIONS EACH CANDIDATE SHOULD BIZ PREPARED T0 PRODUCE, UPON REQUEST. HISIIIER LIBRARY/AMS CARD. 2. READ AND OBSERVE THE FOLLOWING RULES: No candidate shall be permitted to enter the examination room afier the expiration of one-half hour, or to leave during the first half-hour of the examination. Candidates are not permitted to as}: questions ofthc invigilators, cxcqat in cases of supposed errors or ambiguities in examination questions. CAUTION - Candidates guilty of any of the following, or similar, dishonest practices shall be immediately dismissed [ram the examination and shall be liable to disciplinary action. (:1) Making use of any books, papers or memoranda, OLI'ICI’ than those authorized by the examiners. 0:) Speaking or communicating with olhcr candidates. (e) Purposer exposing written papers to the view of other candidates. The plea of accident or forgetfuloess shall not be received. I. CHEMISTRY 205 - Final Examination. April 2000 INFORMATION GIVEN: p. = 3.3 :4 JK-imol-1: 0.0010 Lalm K"mol" M = "’0' L“ 102:0.093 lLalm.=IOI.3J K = 0°C + 273 F - 96.500 c mo!" SOME FAMILIAR EQUATIONS: m conditions to which they apply am NOT specified hm. J 1 211-I_I Tq' n_l =(n-1)kn1; [1/2 = —T_l whcrcn=2, 3... 028 l 2 (P+—)(V-nb)= nRT PV=—nN mfi 2 . V a AE=AH—A(PV) 053— AG°=-RT Ianq _ AH u: = "ms-an as: nCv lnT—Z-HIR [mg mg = - W" (i-L) n VI p. R T1 12 - ‘5 (RT AC=VAP-SAT AH=q,=J'nC.dT k=Ae 3 See" I 30cc" - .0315?an at 298 K AG =— IIFE = Wu“ 1" . . I” 1 v '1 - _ A” .. ST-So-ST- InfiKs)—+ f + nCp(|)g+ V + Intptg)? o Tr Tf TV TV l. The following kinetic data were obtained for the decomposition of ammonia on a heated tungsten surface at 200°C. Initial Press(mmHg): 65 105 150 185 mlf-liquec) : 290 469 670 826 Show how you would determine the order of the reaction and the rate constant. kinetic order = k = 2. The half-life for the acid catalyzed hydrolysis of sucrose to glucose and fructose at 25°C is constant at 500 minutes at a constant pH = 5.0. At the same temperature but at a constant pH - 4.0, the half-life is constant at 50 minutes. Explain briefly how you would deduce what m and it must he in the rate law and mlculate the rate constant, k —d[sucrose]/dt = k [Sll<3r08*3]m[1'l+]n Given the following mechanism for the thermal decomposition of nitryl chloride, k: NO-zCl —) N0: + Cl (slow step) k2 N02Cl + Cl —) N0; + Cl; (fast step) a.) Write a steady state aSSumption equation for the chlorine atom concentration: d[Cl]/dt = b.) Show that the empirical first order rate constant for the disappearance of N02Cl can be identified with 2k. . In the multiple choice questions below, circle the answer(s) that correctly completes the statements (NOTE there maybe more than one correct answer to each statement). a.) The kinetic order of an elementary step in a mechanism is... wewwr always determined by the stoichiometry of the products. not necessarily related to the stoichiometry of the reactants. the "moleeularity" of the elementary step. necessarily an integer number. possibly fractional. b.) In Michaelis-Menten enzyme kinetics... 999w at low concentrations of substrate the reaction is first order in substrate at high concentrations of substrate the reaction is first order in substrate the k, (or k; ) step in the mechanism is unimolccular plots ofV vs [S] are linear Lineweaver-Burke plots require more enzyme than in M—M plots for determining Km. e.) In a simple P vs 1' phase diagram... PPS-"l" the locus of points that constitute the phase boundary equals dP/dT the locus of points that constitute the phase boundary equals AHITAS the phases are not in equilibrium at the triple point the free cnergy‘s are the same for the phases at the phase boundary the entropy's are the same for the phases at the phase boundary 5. One mole of a monatomic ideal gas, initially at 300K and I tum, is heated to 400K. Calculate q. w. AB. and AH when this change is performed in each of the following ways: a.) at constant volume: b.) at constant pressure (1 atm) \V = AE- AH= 5. c.) by adiabatic compression; 5. d.) What is the 218,,5 for part 53. and 5!). above? in pan 53.) A5,), = In part 5b.) A8,.“ = 6. The normal boiling point of chloroform (CI-ICIJ) is 62°C and its molar heat of vaporization is 42 kJ mol". If one mole of liquid chloroform at 62°C and 1 atm. pressure is heated and evaporated isothermally and completely against a constant external pressure of 1 atm. . Calculate q, w, AE, AH. A5,.w , AS...” , and AG for the process. AH = as,” Aston! = AG= 7. a.) Determine the equilibrium constant (KP) at 25"C for the reaction, Br; (3) + C120 (g) 2—» szo + Cl} (8) given the following data for the standard enthalpies of fonnation and the standard third law entropic: (all at 25"C). Br2(g) ohms) BrzO (g) Clzts) Ammo mol") 80.0 76.0 s° (J K" moi") 231.0 200.0 253.0 175.0 K, = 7. 1:.) Indicate the spontaneous direction of this process for a reaction mixture Defined by the partial pressures: Br; (0.5 atm), C120 ( l .0 atm). Brzo (5.0 atm) and C12 (10.0 am) Show all calculations. 8. State the conditions which are necessary for the equations to be TRUE, by cleanly checking the appropriate squares: (I) always (2) at constant T (3) at constant T and P (4) for ideal gases (5) under reversible conditions. (NOTE : there may be more than one necessary condition) lAlw. T m I G Rm. 8) AH = 9» w I...- c) q = -w (for PVT changes in gases) a) as» III-- e) bawdqu . ---- 9 mm = P2Vz 9 We III-- h) AS = nR lnmlv.) g 0 1 - . o I. 9. The combustion (ie oxidation) of methane to carbon dioxide and water.. CH4 (8) + 202 (s) '9 C02 (3) + 21120 (I) shown from tables to have a AG"rm = ~8l8 1:]. It is proposed to use methane in an elecnocltemical fuel cell. With basic electrolyte the half cell reactions are... 0114(3) + SOH'(aq) -> C02 (3) + 614200) +8e' 12°=? 11202 (g) 4’ Hzo (I) + 26-9 20l-l' (aq) E“=+0.401v a.) Calculate the standard cell voltage for the file] cell b.) Calculate the standard reduction potential ofthe C0;:'CH.. half cell above. c.) What is the maximum electrical work that could be obtained from one mole of methane gas? ...
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This note was uploaded on 07/12/2008 for the course CHEM 205 taught by Professor Burnell during the Winter '07 term at UBC.

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