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Unformatted text preview: Chem 120B Problem Set 2 Due: February 5, 2010 1. Problems 17-8 and 17-43 in McQuarrie & Simon’s Physical Chemistry textbook. For problem 17-8, note that the two spin states of a proton in a magnetic field have energies ± planckover2pi1 γB z / 2 . Calculate the field strength B z for which the number of protons aligned with the field is twice that of protons aligned against the field, N w = 2 N o , at T = 300 K . 2. Consider a particle of mass m in a uniform gravitational field. Its potential energy is E ( h ) = mgh , where h is the height above sea level and g is the earth’s gravitational constant, g = 9 . 8 m/s 2 . (i) According to the Boltzmann distribution, what is the probability p ( h ) of finding the mass at height h , relative to the probability p (0) of finding it at sea level ( h = 0 ), at temperature T ? (ii) Now imagine that there are N such masses, all identical and non-interacting. On average, how many of these objects reside at height h , relative to the number at sea level? Express your answer in terms of relative densities, ρ ( h ) /ρ (0) , where ρ ( h ) denotes the number of masses per unit volume at height h ....
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