Vapor Pressure Apparatus for General Chemistry We have developed a simple apparatus for collecting vapor pressure data which we use in a freshman chemistry experiment for the determination of the heat of vaporization of water via the Clausius Clapeyron equation. Operation of the equipment is very simple, and it is safe for use by freshmen. Procedure for use of the apparatus is as follows. Place 200 ml of Hz0 in the vacuum flask and boil for several minutes, with the stopper sitting lightly in place, to flush air from the system. Turn off the hotplate and, as boiling stops, push the stopper into the flask. As the flask cools, measure h (see diagram) a t several temperatures. (With a 20-in. manometer, the temperature can be lowered to about 80°C.) When finished, carefully break vacuum by rocking the stopper. It is easy for students to do several trials, since the water need heanly reboiled and the process repeated. An advantageof the large volume of water used is that it cools quite slowly, giving students plenty of time to take data. Student results using the equipment have heen quite goad, especially considering the simplicity of the experiment and the approximations involved.
~ ( P - ~ oc o
mm
m
son
s106m1 mx
Joseph W. Long Broome Community College Binghamton. NY 13902
Volume 59
Number 10
October 1982
933
