Two-Dimensional Behavior of Methanol Adsorbed on Spheron 6 Graphite Edwin F. Meyer and Mary Prwt Bojan DePaul University, Chicago, IL 60614
The model of avapor adsorbed a t a surface behavinglike a two-dimensional gas is a fascinatine - one.. but one that has not found its w& into standard undergraduate physical chemistry textbooks. The necessary background is there, however (see, e.g., Levine ( I ) ) ,and the purpose of this article is to make teachers of physical chemistry aware of the pedagogical advantages of comparing two- and tbree-dimensional gases and to encourage the performance of these kinds of experiments as appropriate undergraduate research projects. The following derivation is all that is required - simple t o take us from the adsorption isotherm to the properties of the "two-dimensional gas." When a Dure vaoor is in eouilibrium with its adsorbed stntr a t constant temperature and pressure, the chemical notent~alof t11,th uhaies must he euunl. If the uressure of the to produce change in its ;apor is ~han~ed'infinitesimall~ chemical potential, dp,, that of the surface phase must change by an equal amount, dp,, in order to maintain equilibrium,
a
dr. = dr.
Hill (2) has shown that this condition may he written
- & I T + V,dP = -S,dT
+ V,dP + Adn
where the bars sienifv .. . molar auantitiesand A and a represent area and tw
