HFMoleculePopDistEPSolnME501F2011

HFMoleculePopDistEPSolnME501F2011 - ME 501 Thermodynamic...

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ME 501 Thermodynamic Properties and Population Distributions for Diatomic Molecules Example Problem One (1.0) kmol of gaseous HF is contained in a rigid tank at pressure of 0.1 Pa at a temperature of 10 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 Solution:  3/2 22 ,2 ,1 2 1 () : 33 ln ln ln ln ln 30 10 30 HF B HF B tr tr tr tr tr B B B tr tr B B B a Translational Mode mkT mk Z ZT hh Z E U Nk T Nk T Nk T TT U U Nk T T Nk K K Nk     
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HFMoleculePopDistEPSolnME501F2011 - ME 501 Thermodynamic...

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