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Unformatted text preview: kamalska (mk23835) HW03 Quigley (104001) 1 This printout should have 30 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. 001 10.0 points For the reaction A products , the following data were collected. time, s [A] t , M 1.00 1.00 0.430 2.00 0.270 3.00 0.200 4.00 0.160 What is the halflife for this reaction? 1. 1.08 s 2. 0.752 s correct 3. 0.922 s 4. 0.521 s Explanation: 002 10.0 points Consider the concentrationtime dependence as shown below for two first order reactions. [A] Molar Concentration of Reactant Concentration Time Which reaction has the greatest t 1 / 2 ? 1. the reaction represented by the lower curve 2. the reaction represented by the upper curve correct 3. Unable to determine Explanation: 003 10.0 points The reaction 2 HI H 2 + I 2 has rate constants k 1 = 9 . 7 10 6 M 1 s 1 and k 2 = 0 . 097 M 1 s 1 at T 1 = 326 . 85 C and T 2 = 526 . 85 C. What is the activation energy of this reaction? 1. 7 . 93 10 3 J 2. 2 . 86 10 4 J 3. 1 . 84 10 5 J correct 4. 6 . 59 10 4 J 5. 7 . 16 10 7 J Explanation: k 1 = 9 . 7 10 6 M 1 s 1 k 2 = 0 . 097 M 1 s 1 T 1 = 326 . 85 C + 273 . 15 = 600 K T 2 = 526 . 85 C + 273 . 15 = 800 K R = 8 . 314 J mol 1 K 1 The Arrhenius equation gives ln K = lnA E a RT , which is of the form y = c mx , so E a R is the slope of the line ln K vs 1 T . This slope can be estimated from E a R = ln k 1 ln k 2 1 T 1 1 T 2 = ln(9 . 7 10 6 ) ln(0 . 097) 1 600 K 1 800 K kamalska (mk23835) HW03 Quigley (104001) 2 = 22104 . 8 K E a = R ( 22104 . 8 K) = (8 . 314 J mol 1 K 1 ) ( 22104 . 8 K) = 1 . 83779 10 5 J / mol . 004 10.0 points We wish to find the specific rate constant for the reaction A products . After 5 minutes the amount of A has de creased from 2 . 3 mol / L to 1 . 3 mol / L. Find k using minutes as the time scale. The reaction is second order in [A]. Correct answer: 0 . 0668896 L mol 1 min 1 . Explanation: [A] = 2 . 3 mol / L [A] t = 1 . 3 mol / L t = 5 min Since time and concentration are involved, the integrated rate equation is used. For second order, 1 [A] t 1 [A] = ak t k = 1 at parenleftbigg 1 [A] t 1 [A] parenrightbigg = 1 5 min parenleftbigg 1 1 . 3 mol / L 1 2 . 3 mol / L parenrightbigg = 0 . 0668896 L mol 1 min 1 005 10.0 points The graph describes the energy profile of a reaction. A B Time Energy(kJ) 50 300 400 What are the values for H and E a , respec tively, for the reaction in the direction writ ten? 1. 250 kJ, 350 kJ correct 2. 250 kJ, 350 kJ 3. 250 kJ, 100 kJ 4. 250 kJ, 100 kJ 5. 250 kJ, 100 kJ Explanation: E a H A B Time Energy(kJ) 50 300 400 H = 300 kJ 50 kJ = 250 kJ E a = 400 kJ 50 kJ = 350 kJ 006 10.0 points A nonsteroidal antiinflammatory drug is me tabolized with a firstorder rate constant of 3.25 day 1 . What is the halflife for the...
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This note was uploaded on 11/03/2008 for the course CHEM 104 taught by Professor Quigley during the Spring '08 term at CUNY Hunter.
 Spring '08
 QUIGLEY
 Reaction

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