Physical Chemistry exam 2 - Chem142 – Introduction to Physical Chemistry Exam#2(50 minutes Name 100 points Units and Constants R = 8.314 J/K*mol =

Physical Chemistry exam 2 - Chem142 – Introduction to...

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Chem142 – Introduction to Physical Chemistry Exam #2 (50 minutes) Name ______________________ 100 points March 17, 2017 Units and Constants R = 8.314 J/K*mol = 0.08314 L*bar/K*mol = 0.08206 L*atm/K*mol k B = 1.38*10 -23 J/K N A = 6.022*10 23 mol -1 1 dm 3 = 1 L K = 273.15 + °C 1 bar = 100 kPa = 0.986 atm 1 atm = 101.325 kPa = 760 torr 1 L*atm = 101.325 J Equations phase transition phase transition 1 T m H dP dT V T 2 1 2 1 1 ln ln VAP VAP VAP H P P R T H S P RT R     2 rms nMv P 3 3 3 3 2 2 2 rms B rms A V RT v M KE nRT k T v PN z RT         0 ln 2 1 1 1 / 1 ln / 0 1/2 1/2 0 0 0 0 0 A A e t k kt A A t A k B B kt B A A A kt * * 2 * 2 i i i f f solvent fus f fus b b solvent vap b vap solute P x P T iK m M RT K H T iK m M RT K H V in RT   * . . J D conc grad n JAt 2 6 B d Dt k T D r          0 0 0 2 1 2 1 k E S rate K S k k K k m m / k Ae a E RT * * * * A total B A total A B P P P y P P P 1 _______/30 2 _______/23 3 _______/13 4 _______/14 5 _______/20 total _______/100 page 1
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#1. Short answer/multiple choice questions. (30 points total) a) (6 points) Given the phase diagram to the right, answer the following questions: B If the pressure is increased, the freezing point of the solid will a) increase b) decrease c) be unchanged A If the pressure is increased, the sublimation temperature will a) increase b) decrease c) be unchanged If the temperature is increased, the vapor pressure of the liquid will a) increase b) decrease c) be unchanged A b) (12 points) Chlorofluorocarbons (CFCs) play a major role in chemistry occurring in the stratosphere. Specific examples of CFCs include CFCl 3 , CF 2 Cl 2 , and C 2 F 3 Cl 3 . The temperature near the top of the stratosphere is 270 K. E What is the root-mean-square speed of CF 2 Cl 2 (120.9 g/mol) at the top of the stratosphere? a) 0.746 m/s b) 0.236 m/s c) 23.6 m/s d) 7.46 m/s e) 236 m/s D Which of the 3 gases will have the largest kinetic energy (per mole) at 270 K? a) CFCl 3 b) CF 2 Cl 2 c) C 2 F 3 Cl 3 d) all the same KE Which of the 3 gases will have the narrowest distribution of speeds at 270 K? a) CFCl 3 b) CF 2 Cl 2 c) C 2 F 3 Cl 3 d) all the same distribution C The collision cross-section for C 2 F 3 Cl 3 is approximately twice that for CFCl 3 . What is the ratio of the mean free path of CFCl 3 to the mean free path of C 2 F 3 Cl 3
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