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Unformatted text preview: krohn (tek335) H14: Kinetics 1 Mccord (52445) 1 This printout should have 16 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. 001 10.0 points The rate of the reaction 2 O 3 3 O 2 is equal to 1. 1 3 [O 2 ] t . 2. 1 2 [O 3 ] t . correct 3. [O 3 ] t . 4. [O 2 ] t . 5. + 1 2 [O 3 ] t . Explanation: The rate of a chemical reaction can either be expressed as the rate of disappearance of a reactant (as in this case) or as the rate of appearance of a product. However, this rate is multiplied by the inverse of the coef ficient of the species in question. The nega tive sign here reminds us that as the reaction progresses, this species is consumed and de creases in concentration. 002 10.0 points When the reaction 3 NO(g) N 2 O(g) + NO 2 (g) is proceeding under conditions such that 0.015 mol/L of N 2 O is being formed each second, the rate of the overall reaction is ? and the rate of change for NO is ? . 1. 0.015 M s 1 ; +0.045 M s 1 2. 0.030 M s 1 ; 0.005 M s 1 3. 0.015 M s 1 ; 0.005 M s 1 4. none of the other answers is correct 5. 0.015 M s 1 ; 0.045 M s 1 correct Explanation: Notice that three moles of NO are required to make one mole of N 2 O in this reaction, so the rate of disappearance of NO (which has a negative sign) is three times the rate of appearance of N 2 O. 003 10.0 points Consider the irreversible reaction A + 2 B 3 C . Which of the following correctly expresses the rate of change of [B] ? 1. [B] t = 1 2 (rate of rxn) 2. [B] t = +2 (rate of rxn) 3. [B] t = (rate of rxn) 4. [B] t = + 1 2 (rate of rxn) 5. [B] t = 2 (rate of rxn) correct 6. [B] t = +(rate of rxn) Explanation: As B is a reactant and consequently disap pears during the reaction, its rate of change will be negative and the inverse of the coeffi cient is used when writing the rate: (rate of rxn) = 1 2 [B] t 2 (rate of rxn) = [B] t 004 10.0 points Suppose a compound is involved in three different reactions denoted R 1 , R 2 , and R 3 . Tripling the concentration of this reactant in all three reactions causes the rates of reaction to increase by factors of 3, 9, and 1, respec tively. What is the order of each reaction with respect to this reactant? krohn (tek335) H14: Kinetics 1 Mccord (52445) 2 1. R 1 = 0; R 2 = 1; R 3 = 2 2. R 1 = 2; R 2 = 0; R 3 = 1 3. R 1 = 3; R 2 = 9; R 3 = 1 4. R 1 = 1; R 2 = 2; R 3 = 0 correct 5. R 1 = 1; R 2 = 3; R 3 = 0 Explanation: Tripling the concentration of the reactant in R 1 brings about a tripling (= 3 1 ) increase in the rate of the reaction, so the reaction is first order with respect to the reactant in this case....
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This note was uploaded on 10/25/2010 for the course CH 302 taught by Professor Holcombe during the Spring '07 term at University of Texas at Austin.
 Spring '07
 Holcombe
 Kinetics

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