NS102-200901-ProblemSet6

# NS102-200901-ProblemSet6 - NS102 Study Problems Set 6 The...

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NS102 Study Problems Set 6 The set contains study problems and exam questions from the previous semesters on kinetics and rate laws. 1. (Exam Archive) The rate of consumption of B in the reaction 2A + 3B + C 4D + 2E is 2.4 mol L -1 s -1 . State the rates of formation and consumption of A, C, D, and E. Answer: Rate of consumption of A=1.6 mol L -1 s -1 Rate of consumption of C=0.8 mol L -1 s -1 Rate of formation of D=3.2 mol L -1 s -1 Rate of formation of E=1.6 mol L -1 s -1 2. At 1000 °C cyclobutane (C 4 H 8 ) decomposes in a first order reaction with the very high rate constant of 87 s -1 , to two molecules of ethylene (C 2 H 4 ). a) If the initial cyclobutane (C 4 H 8 ) concentration is 2.00 M, what is the concentration after 0.010 s? b) What fraction of cyclobutane (C 4 H 8 ) has decomposed in this time? Answer: a) 0.83M b) 0.58 or 58% 3. (Exam Archive) In a first-order decomposition reaction, 50% of a compound decomposes in 10.5 min. a) What is the rate constant of the reaction? b) How long does it take for 75 % of the compound to decompose? Answer: (a) k=0.001 s 1=0.07 min –1 (b) t=19.8 min 4. (Exam archive) For the simple decomposition reaction AB(g) A(g)+B(g) , Rate=k[AB] 2 and k=0.2L/mol.s a) How long will it take for [AB] to reach one-third of its initial concentration of 1.0 M? b) What is [AB] after 15 seconds? (Show your work) Answer: (a) t=10 seconds (b) [A]=0.25 M 5. Many gaseous reactions occur in a car engine and exhaust system. One of these is mn 2 2 2 2 NO (g)+CO(g) NO (g)+CO (g) rate=k[NO ] [CO] . Use the following data to determine the individual and overall reaction orders Experiment Initial Rate (mol/L.s) Initial [NO 2 ] (mol/L) Initial [CO] (mol/L) 1 0.0050 0.10 0.10 2 0.080 0.40 0.10 3 0.0050 0.10 0.20 Answer: The reaction is 2 nd order in NO 2 , zero order in CO. Rate Law is rate=k[NO 2 ] 2 [CO] 0 =k[NO 2 ] 2 .The reaction is 2nd order overall 6. (Exam Archive) For the reaction 4A + 3B 2C , the following data were obtained at constant temperature: Experiment Initial Rate (mol/L.min) Initial [A] (mol/L) Initial [B] (mol/L) 1 5.0 0.10 0.10 2 45.0 0.30 0.10 3 10.0 0.10 0.20 4 90.0 0.30 0.20

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a) What is the order with respect to each reactant? What is the overall order? b) Write the rate law. c) What is the rate constant k? Answer : (a) 2 nd order in A, 1 st order in B, 3 rd order overall; (b) Rate=k[A] 2 [B]; (c) k=5000 L 2 mol -2 s -1 7. (Exam Archive) A key step in the formation of acid rain is the following reaction between oxygen and nitric oxide 22 2NO + O 2NO , The data on the right were obtained at constant temperature for this reaction: a) What is the order with respect to NO and O 2 ? What is the overall order? b) Write the rate law? c) What is the rate constant k? Answer: (a) 2 nd order in NO, 1 st order in O 2 and 3 rd order overall (b) Rate=k[NO] 2 [O 2 ] (c) k=17.2 L 2 /mol 2 .min 8. (Exam Archive) For the reaction (g) (g) (g) A +B AB the reaction rate is 0.20 mol/L.s when 0 0 A = B = 1.0 mol/L         . If the reaction is first order in B and second order in A, what is the rate when   0 A = 2.0 mol/L and   0 B = 3.0 mol/L .
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## This note was uploaded on 12/23/2011 for the course NS 102 taught by Professor Alimetozen during the Spring '09 term at Sabancı University.

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NS102-200901-ProblemSet6 - NS102 Study Problems Set 6 The...

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