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Transcript of CHL721_HW7
CHL721 Adv Chem Engg Thermodynamics
HW #7 Due date: 13th April, 2015 (in lecture)
TB1: Modern Stat. Mech., Chandler, 1st Ed.
Q1-‐9. TB1:: Ex. 3.5, 3.6, 3.8, 3.9, 3.12, 3.18, 3.19, 3.20, 3.22
Q10. The elasticity of a rubber band can be described in terms of a 1D model of a chain made up of N (>>1) segments of length a. Each segment has just two states— a horizontal orientation and a vertical orientation. At a given tension f and temperature T, the chain length L (distance between two ends) is nx. You can assume that the joints turn freely and both states of segment are equally likely in absence of tension. Now answer the following:
(i) Obtain the equation of state (EOS) for the above chain, i.e., a relation between f, T and nx. (Hint: under the action of stress, there is an energy difference between the vertical and horizontal orientation states).
(ii) Under what conditions does your EOS leads to Hooke’s law?
Q11. A useful way to cool He3 is to apply pressure P at sufficiently low temperature T to a co-‐existing liquid-‐solid mixture. Describe qualitatively how this works on the basis on the following assumptions:
(a) The molar volume of the liquid VL is greater than that of the solid VS at all temperatures.
(b) The molar liquid entropy is given by
𝑆! = 4.6𝑅𝑇
(c) The entropy of the solid SS comes entirely from the disorder associated with the nuclear spins ± !
!.
Based on the above information, also include a a semi-‐quantitative graph of the p-‐T diagram of He3 at low temepratures.
(Hint: use the Clausius-‐Clapeyron equation).