Homework 4 Key

Homework 4 Key - CHEMISTRY 201X: Homework #4 "Phase...

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CHEMISTRY 201X: Homework #4 Due : Monday, October 1, 2007 “Phase Diagrams and Transitions; Vapor Pressure” (1) (16 points) (a) (4 pts) Using the following information, sketch the phase diagram for ammonia for pressures between 0 and ca. 1.2 atm and for temperatures between 0 and 300 K. Label important points on this curve and phases existing in each region. Normal melting point = 78 ° C Heat of Fusion = 5.65 kJ/mol Normal boiling point = 33.5 ° C Heat of Vaporization = 23.36 kJ/mol Triple Point Temperature = 78.2 ° C Density of NH 3 (s) near n.m.p. = 0.833 g/cm 3 Pressure at Triple Point (s, l, g) = 45.6 torr Density of NH 3 (l) near n.b.p. = 0.682 g/cm 3 (b) (2 pts) Use the Clausius-Clapeyron equation to predict the pressure at the triple point given the normal boiling point of ammonia and the triple point temperature. Compare your result with experiment. ln(p 1 /1 atm) = (23360 J/mol / 8.314 J/mol K)[(1/239.65 K) (1/194.95 K)] p 1 = 0.068 atm = 51.7 torr (c) (4 pts) Assuming that the densities of liquid and solid ammonia do not change with temperature or pressure, estimate the slope of the line for equilibrium between solid and liquid phases. You may assume that the solid Z ZX YZZ liquid equilibrium line remains straight.
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This homework help was uploaded on 03/27/2008 for the course CHEM 201 taught by Professor Miller during the Fall '07 term at Iowa State.

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Homework 4 Key - CHEMISTRY 201X: Homework #4 "Phase...

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