103B Exam 1-A

103B Exam 1-A - Exam I master Page 1 Chemistry 103B Exam 1...

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Page 1 Exam I master 4/10/2008 12:18:55 AM http://www.chem.arizona.edu/~kellerp/exams/Exam1/Exam1Aan/Exam1Aan.htm Chemistry 103B Exam 1 Answer Key Form A 1. (2) A reaction has just one elementary step , C + C C 2 [slow]. The rate constant k has the value 7.1 x 10 -2 L/mols. At the start of the reaction (t = 0) the concentrations of C and C 2 were 0.300mol/L and 0 mol/ L, respectively . What is the concentration of product after 180. seconds ? The slow step is bimolecular (the units of k tell you this as well). Application of the bimolecular integrated rate law gives the concentration of reactant C after 180s: The concentration of C decreases by 0.300 0.062= 0.238mol/L. The concentration of product increases by half that: 0.119mol/L (a) 0.062mol/L (b) 0.238mol/L (c) 0.119mol/L (d) 0.031mol/L (e) 0.000mol/L 2. (2) Carbon-14 is a radioactive isotope with a half lifeof 5730years. What is the rate constant for its decay in units of years -1 ? (a) 5.25 x10 -5 (b) 3.49 x10 -4 (c) 1.75 x10 -4 (d) 3.97 x10 -4 (e) 1.21x10 -4
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Page 2 Exam I master 4/10/2008 12:18:55 AM http://www.chem.arizona.edu/~kellerp/exams/Exam1/Exam1Aan/Exam1Aan.htm (a) 5.25 x10 -5 years -1 (b) 3.49 x10 -4 years -1 (c) 1.75 x10 -4 years -1 (d) 3.97 x10 -4 years
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103B Exam 1-A - Exam I master Page 1 Chemistry 103B Exam 1...

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