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Unformatted text preview: Chem33-1, C-hour Problem Set 2 Due Date: Oct. 5, 2007 Student name: ___________________ Student SISD #: __________________ 1. Which of the following involve an increase in the entropy of the system under consideration? a. melting of a solid e. mixing b. evaporation of a liquid f. separation c. sublimation g. diffusion d. freezing ANSWER: Of the three phases, solids are most ordered and gases are most disordered. Thus, a, b, c, e, and g involve an increase in entropy. All others decrease disorder and entropy. 2. Entropy can be calculated by a relationship proposed by Ludwig Boltzmann: S = k B ln Ω Where k B = 1.38 x 10-23 J/K and Ω is the number of ways a particular state can be obtained. (This equation is engraved on Boltzmann's tombstone.) Calculate S for the three arrangements of particles in Table 10.1 of our text book. ANSWER: Arrangement I: S = k ln Ω with Ω = 1 S = k ln 1 = 0 Arrangement II: Ω = 4: S = k ln 4 = 1.38 x 10-23 J/K ln 4 S = 1.91 x 10-23 J/K Arrangement III: Ω = 6: S = k ln 6 = 2.47 x 10-23 J/K Alternatively, you could have calculated the entropy based on the probabilities for each arrangement in table 10.1. In this case you would have gotten the probabilities 1/16, 4/16, and 6/16. As a consequence the absolute values of the entropy would have been shifted but the differences between them would remain unchanged. 3. Calculate the energy required to change the temperature of 1.00 kg of ethane (C 2 H 6 ) from 25.0 o C to 73.4C to 73....
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This note was uploaded on 04/29/2008 for the course CHEM 33 taught by Professor Rose-petruck during the Fall '07 term at Brown.
- Fall '07