cem152-ss08-key-exam2A - Name: 2 , ‘ 69‘ L CEM 152 3308...

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Unformatted text preview: Name: 2 , ‘ 69‘ L CEM 152 3308 PID: : {\t ' l "4 Exam 2A—February 20,2008 Answer each question in the space provided. Clearly mark your final answer. Show all work for full credit. 1. (12 pts) A certain first-order reaction has k =.2.75 x 10'2 s'1 at 20 °C. What is the value of k at 60 °C, if Ea =—: 105 kJ/mol? \ .__ g“: mqooo 3 AM QANMW, E17 J..- Z)? R: QtaM‘J/MLW T2, K T), h '1 T‘1m”cfy)_73:2°\p$lL unto-2s“) ‘bwéofl/MG. (L fin, Qo°c+a7% 9339* KL 6 K3le gaav‘fig 1 Pl "' g - , fin —. z-ut‘mu K..L\.o°l‘l¥l\9 Hi4 \) 04L -2 —’ . Zns‘rIO S =— "3‘11 KL ) e. -‘z 4 ~\ Wm” 5.. orgasm {LL = 9.31 s a; 2. (10 pts) In lecture, the kinetics of the dissociation of thiosulfate ion (82032’) by strong acid (IT) was explored. The reaction was found to be independent of [W]. In the space below, make a plot of [PF] vs. time to schematically show how concentration varies with time for a zeroth order process. {Ml jg: wt 3. ( 12 pts) Clearly mark whether each of the following statements, regarding rate constants, are true or false?- “ a. A reaction having a rate constant with units M’ls'1 is third order. F b. At a given temperature, the rate constant varies with reactant concentration. «F c. As the activation energy of a reaction increases, the rate constant typically F decreases. d. For reactions in equilibrium, the rate constants are equal. Name: _ CEM 152 3508 PID: ‘ liefl ' QML Exam 2A—February 20,2008 4. (12 pts) The oxidation of SO; to $03 is catalyzed by N02. The reaction is believed to proceed as follows: I. N02(g) + 302(g) —+ N0(g) + 803(g) 11- 2N0(g) + 02(g) —> 2N02(g) Give the overall'oxidation reaction based on the two mechanistic steps. 35065} O; «a 3.80; What is the rate law for the reaction assuming step I. is rate determining. L: [M03 {CO «Cl 5. (10 pts) The following data were measured for the reaction BF3(g) + NH3(g) ’9 FsBNH3(g) [NHs] (M) Find the order of the reaction with respect to [BF3]? ~— m. » r n. , __ Rage/L, iL LEE) LN Hg) : 0,0935 — was a is Lemmtwa“ —. 0 as“? [0‘1CP6W‘ : J—m m a \ mammaw‘ (:53 ' ; 3 6. (12 pts) Clearly mark whether each of the following statements, pertaining to colligative properties, is true or false. F, a. If an aqueous solution of sucrose boils at 106 °C, it will freeze at —6 °C. b. The boiling point of a solution will increase if the molal concentration of T solute is increased 0. A water solution with a high osmotic pressure will have a higher vapor i: pressure at a given temperature than a water solution with a lower osmotic pressure. F (1. At equal low molal concentrations, calcium chloride and ethanol will have the same effect on the fieezing point of water. ‘ Name: . , p h" L - CEM 152 $308 PID: u ‘l \ Exam 2A — February 20, 2008 7. (10 pts) The vapor pressure curve for liquid hexane is provided below. Sketch on the same plot the vapor pressure curve that would result if a small amount of solid solute, were added to the pure solvent. 4000 --—--- Liquid hexane VP. cwvfi WM be \aweve A v S \Am 92 0* COG/“e \ 'Wx“ Qb‘k gaml qur Pressure (rim H91 8 8 8. (12 pts) A generic reaction coordinate diagram is given to the right. Determine Whether each of the following statements about the diagram is true or false. “T” a. Point W is the transition state. T b. U will deCrease with addition of a catalyst. F c. The reaction from Y -> X is exothermic. K? d. The reaction rate for Y—> X is faster than the rate for X ——> Y. Readion Pathway 9. (10 pts) The decomposition of SOZC12(g) into 802(g) and C12(g) is first order in [30202]. At 320 °C, the rate constant is 2.2 x 10‘1 s'l. A container at 320 °C is initially charged with 375 torr 802C12. How much of the gas remains after 20 s? Jufisozcra : AM: + £ow (1980 Rim-$391697. 3 ' lil’doA 5 )7 + Q“ G7: W) 2 ~ HH 4 €90, Q» PM. 3 @4152 ...
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cem152-ss08-key-exam2A - Name: 2 , ‘ 69‘ L CEM 152 3308...

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