Exam2ME501F2007 - 1 Name_ ME 501 Exam #2 November 15, 2007...

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1 Name___________________________ November 15, 2007 Prof. Lucht ME 255 1. POINT DISTRIBUTION Problem #1 40 points _________________ Problem #2 30 points _________________ Problem #3 30 points _________________ 2. EXAM INSTRUCTIONS Write your name on each sheet. This exam is closed book and closed notes. Major hint: When calculating partition functions using the formula  exp / jj B j Z gk T  , write down the individual terms in the summation: you will need them later to calculate populations and properties. Several equation sheets are attached. When working the problems, list all assumptions, and begin with the basic equations. If you do not have time to complete evaluation of integrals or of terms numerically, remember that the significant credit on each problem will be given for setting up the problem correctly and/or obtaining the correct analytical solution. ME 501 Exam #2
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2 ME 501 Exam #2 11/15/2007 Name___________________________ 1. (40 points) One (1.0) kmol of gaseous HF is contained in a rigid tank at pressure of 0.1 Pa at a temperature of 20 K (state 1). The temperature of the tank is raised to 30 K (state 2) by heat transfer. The pressure is low enough that the HF exhibits ideal gas behavior. Assume that the translational mode is fully excited at both the initial and final states. (a) Assuming that HF is a rigid-rotator, calculate the internal energy change U 2 U 1 (in J) for the constant volume heating process. Only the first four rotational levels ( J = 0, 1, 2, 3) need to be considered for this problem; explain why this is so . Do not assume that Z T rot rot / . What is the rotational contribution to the internal energy change? Neglect the contributions of the vibrational, electronic, and nuclear modes. (b) Calculate the entropy change S 2 S 1 (in J/K) for the gaseous HF. Use the same assumptions as in part (a). Again, do not assume that Z T rot rot / . For HF: rot K 30 , ma m u 20
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3 ME 501 Exam #2 11/15/2007 Name___________________________ Problem #1 Extra Page
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4 ME 501 Exam #2 11/15/2007 Name___________________________ Problem #1 Extra Page
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5 ME 501 Exam #2 11/15/2007 Name___________________________ 2. (30 points) A system has five energy levels with a constant energy level spacing: 100 0,1, 2, 3, 4 j B jK j k  The degeneracy of each level increases with j and is given by  2 10 11 0 j gj  . (a) For an assembly of 10 7 particles, find the assembly energy E (in J) at a temperature of 50 K. Assume corrected-Maxwell-Boltzmann statistics. Note: this system does not have translational, rotational, etc. energy levels. It has only the energy levels specified. (b) For an assembly of 10 7 particles, find the assembly entropy S (in J/K) at a temperature of 50 K. Assume corrected-Maxwell-Boltzmann statistics.
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This note was uploaded on 12/26/2011 for the course ME 501 taught by Professor Na during the Fall '10 term at Purdue University-West Lafayette.

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Exam2ME501F2007 - 1 Name_ ME 501 Exam #2 November 15, 2007...

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