CHEM 01LB Lecture Notes - Lecture 5: Partial Pressure, Dynamic Equilibrium, Vaporization
CHEM 01LB Experiment 5: Vapor Pressure and Heat of Vaporization of Liquids
●Experimental purpose
○The purpose of this experiment is to use vapor pressure to determine the heat of
vaporization of unknown liquids
●Vapor pressure
○Molecules of liquids
and solids
(at nonzero temperatures) are vibrating with
kinetic energy proportional to their temperature
○Dynamic equilibrium: the process of molecules moving from the liquid/solid
phase to the gas phase and back again
○Vapor pressure: the partial pressure of the gas phase portion of a compound
exerted upon the surface of that substance
●Vapor pressure and boiling
○Boiling point: the temperature at which the vapor pressure of the liquid is equal to
the external pressure of the atmosphere above that liquid
○The dependence of vapor pressure on temperature is expressed
thermodynamically as:
■ln VP = -ΔHvap/(RT) + C
●ΔHvap = amount of heat (J) required to vaporize one mole of the
liquid against a constant pressure
○The graph of ln VP vs. 1/T will obtain a straight line
■From the slope of the line, the heat of vaporization of the liquid
Document Summary
Chem 01lb experiment 5: vapor pressure and heat of vaporization of liquids. The purpose of this experiment is to use vapor pressure to determine the heat of vaporization of unknown liquids. Molecules of liquids and solids (at nonzero temperatures) are vibrating with kinetic energy proportional to their temperature. Dynamic equilibrium : the process of molecules moving from the liquid/solid phase to the gas phase and back again. Vapor pressure : the partial pressure of the gas phase portion of a compound exerted upon the surface of that substance. Boiling point : the temperature at which the vapor pressure of the liquid is equal to the external pressure of the atmosphere above that liquid. The dependence of vapor pressure on temperature is expressed thermodynamically as: H vap = amount of heat (j) required to vaporize one mole of the liquid against a constant pressure. The graph of ln vp vs. 1/t will obtain a straight line.
