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, sketchthe 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 NH3(s) near n.m.p. = 0.833 g/cm3Pressure at Triple Point (s, l, g) = 45.6 torr Density of NH3(l) near n.b.p. = 0.682 g/cm3(b) (2 pts) Use the Clausius-Clapeyron equation to predict the pressure at the triple pointgiven the normal boiling point of ammonia and the triple point temperature. Compare your result with experiment. (c) (4 pts) Assuming that the densities of liquid and solid ammonia do not change with temperature or pressure, estimate the slope of the linefor equilibrium between solid and liquid phases.
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