Lecture 21: Vapor Pressure Phase Diagrams: Single components vs. the “real” world Liquids vs. solids and everything in between. Vapor pressure of liquids and solids as a measure of “escaping tendency”

1mL of liquid water is placed into an evacuated container of volume 10mL at room temperature. What is the pressure? (1) 20atm (2) 2atm (3) 0.2atm (4) 0.02atm (5) 0.002atm (6) 0.0002atm

A 1mL vial filled with liquid water is sealed into a container of volume 10mL containing air at 1.0atm and room temperature. What is the pressure after the vial is broken open? (1) 1.20atm (2) 1.02atm (3) 1.00atm (4) 0.20atm (5) 0.02atm (6) 0.00atm

In the “real world” one rarely has only one component Typically some inert or buffer gas is present and may determine the pressure (a blanket, an atmosphere) Sometimes an inert container controls the volume of the system (a flask or bomb) Sometimes an inert container controls the pressure of the system (a balloon or a cylinder and piston) Very often one or more phases is an intimate mixture – a “solution” of components Ask yourself how the single component phase diagrams of each component present apply to the “real world” situation you are dealing with.

Vapor pressure of component tends to increase exponentially with temperature. Why?

Vapor pressure decreases as the mole fraction of component in a solution decreases. Why?

Predict the vapor pressure of 9mol of ether at its normal boiling point if 1 mol of naphthalene is dissolved in the ether? (1) 1.9atm (2) 1.1atm (3) 1.09atm (4) 1.01atm (5) 1.00atm (6) 0.99atm (7) 0.91atm (8) 0.90atm (9) 0.10atm (10) 0.01atm