Midterm+1 - Physics 30 Midterm 1 Spring 2010 Boiling point...

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Physics 30 – Midterm 1 – Spring 2010 Boiling point of water (20 points) Using thermodynamic data from the end of Schroeder’s appendix, consider 1 mole of gaseous vs liquid water: 1. From the relation between H and G, show that the Δ G gl , Δ H gl and S gl (as computed from the table) are self-consistent. I am writing Δ G gl for the free energy different Δ G g - Δ G l ; since this is actually a difference between Δ G’s, chemists often write it as ΔΔ G. 2. Assuming that Δ G, Δ H and S do not change with temperature, calculate the boiling point of water at atmospheric pressure. Your prediction will be too low because G, H and S are not, in fact, independent of temperature. 3. What is the energy difference Δ U gl between gas and liquid water? Since interactions between gas molecules are generally small (and in fact zero in the ideal gas limit), most of this energy difference is caused by interactions in liquid water. Liquid water is actually enormously complex and the interaction energy (or, even worse, the entropy) is very hard to calculate from first principles. Non-symmetric random walk (40 points). Derive the advection-diffusion equation corresponding to a random walk with different-sized steps in the left and right directions: leftward steps of length l occur with probability q and rightward step of length 2l occur with probability p. The time between steps is
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This note was uploaded on 04/15/2010 for the course PHYSICS 420 taught by Professor Lorenzosorbo during the Spring '10 term at Smith.

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Midterm+1 - Physics 30 Midterm 1 Spring 2010 Boiling point...

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