CHM2046Test2 - CHM2046 Test 2 Version A Answers underlined...

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CHM2046 Test 2 Version A Answers underlined 1a) What are the units of k in the following rate law? R a t e = k [ X ] [ Y ] Rate law suggests second order A) M s B) Ms C) 11 Ms D) 2 M s E) 2 s M 2a) Consider the following reaction and its equilibrium constant: S O 2 (g) + NO 2 (g) ֎ SO 3 (g) + NO(g) K c = 0.33 A reaction mixture contains 0.39 M SO 2 , 0.14 M NO 2 , 0.11 M SO 3 and 0.14 M NO. Which of the following statements is TRUE concerning this system? A) The reaction will shift in the direction of reactants. B) The equilibrium constant will decrease. C) The reaction will shift in the direction of products. Q = 0.28 < K D) The reaction quotient will decrease. E) The system is at equilibrium. 3a) Which of the following represents the integrated rate law for a second-order reaction? A) [ ] [] At ln Ao = - k t B) At Ao = kt C) [ ] [ ] = - kt D) k = Ea RT Ae ⎛⎞ ⎜⎟ ⎝⎠ E) 2 1 k ln k = Ea 1 RT + lnA 4a) The first-order rearrangement of CH 3 NC is measured to have a rate constant of 15 1 3.61 10 s −− × at 298 K and a rate constant of 71 8.66 10 s × at 425 K. Determine the activation energy for this reaction. Use the 2 point form Arrhenius eqn = × × K K E a 425 1 298 1 314 . 8 10 61 . 3 10 66 . 8 ln 15 7 () 3 10 00 . 1 314 . 8 30 . 19 × = a E ; a E mol kJ = × × × / 10 00 . 1 ) 1000 ( 314 . 8 30 . 19 3 A) 160. kJ/mol B) 240. kJ/mol C) 417 kJ/mol
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D) 127 kJ/mol E) 338 kJ/mol 5a) Given the following proposed mechanism, predict the rate law for the overall reaction Mechanism A 2 ֎ 2A k -1 , k 1 fast AB A B +→ k 2 slow rate = k 2 [A][B]; but A is an intermediate from the fast equilibrium step. So, k 1 [A 2 ] = k -1 [A] 2 ; [A] = {(k 1 /k -1 )[A 2 ]} ½ ; then sub for [A] in rate eqn above, rate = (k 2 k 1 /k -1 ) [A 2 ] ½ [B] (k 2 k 1 /k -1 ) = single constant, k A) Rate = k[A][B] B) Rate = k[A 2 ][B] C) Rate = k[A 2 ][B] 1 2 D) Rate = k[A 2 ] 2 E) Rate = k [A 2 ] 1 2 [B] 6a) What data should be plotted to show that the experimental concentration data fits a first- order reaction? A) 1/[reactant] vs. ln (time) B) [reactant] vs. time C) ln[reactant] vs. time D) ln(k) vs. 1/T E) ln(k) vs. E a 7a) A plausible two-step mechanism for a reaction is shown below. What is the overall reaction from this mechanism?
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This note was uploaded on 09/21/2009 for the course CHM 2046 taught by Professor Dixon during the Spring '08 term at University of Central Florida.

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CHM2046Test2 - CHM2046 Test 2 Version A Answers underlined...

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