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EXAM202 - Mantooth Marlo Exam 2 Due 1:00 pm Inst Donna C...

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Mantooth, Marlo – Exam 2 – Due: Feb 23 2007, 1:00 pm – Inst: Donna C Lyon 1 This print-out should have 20 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. The due time is Central time. 001 (part 1 of 1) 10 points The reaction N 2 O 4 (g) * ) 2 NO 2 (g) is at equilibrium. Increasing the pressure will have what effect on the equilibrium? 1. The equilibrium remains unchanged. 2. The equilibrium is shifted to the left. correct 3. The equilibrium is shifted to the right. Explanation: Increasing pressure shifts the equilibrium in the direction that produces fewer molecules of gas. 002 (part 1 of 1) 10 points Four of the following factors can affect the for- ward rate of a chemical reaction. Which one cannot affect this rate? Note: The question refers to reaction rate, not equilibrium. 1. physical state or state of subdivision of solid reactants 2. presence of a catalyst 3. temperature 4. removal of some of the products of the forward reaction correct 5. concentration of reactants of the forward reaction Explanation: As long as reactants are present, the for- ward reaction can occur; the higher the re- actant concentration, the faster the reaction can proceed. Other factors which increase reaction rates are increased temperature, in- crease in surface area of solid reactants and the presence of a catalyst. 003 (part 1 of 1) 10 points Consider the reaction 2 HgO(s) * ) 2 Hg( ) + O 2 (g) . What is the form of the equilibrium constant K c for the reaction? 1. K c = [Hg] 2 [O 2 ] 2. K c = [O 2 ] [HgO] 2 3. K c = [O 2 ] correct 4. None of the other answers is correct. 5. K c = [Hg] 2 [O 2 ] [HgO] 2 Explanation: Solids and liquids are not included in the K expression. 004 (part 1 of 1) 10 points The first-order rate constant is k = 3 . 4 × 10 - 3 s - 1 for the decomposition of cyclobutane cyclobutane 2(ethylene) with half-life is 204 seconds. What fraction of a sample of cyclobutane remains after 612 seconds under the specified conditions? 1. fraction = 1 8 correct 2. fraction = 1 3 3. fraction = 1 16 4. fraction = 1 2 5. fraction = 1 6 Explanation: t 1 / 2 = 204 s t = 612 s a = 1 k = 3 . 4 × 10 - 3 s - 1
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Mantooth, Marlo – Exam 2 – Due: Feb 23 2007, 1:00 pm – Inst: Donna C Lyon 2 Make a chart. Time Amount left (cyclobutane = C) 0 C 204 C 2 408 C 4 612 C 8 After 612 seconds, 1 8 of the original amount of cyclobutane is left.
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