The Thermodynamics of Chromatography - Interactions Between the Atoms of Hydrogen, Carbon, Chlorine and Bromine and an Exclusively Dispersive Stationary Phase > Experimental Data > Page 39

 

Conversely, if there is no change in entropy, (i.e., (DSo=0) then,

Thus, to ensure there is no standard energy change when transferring from one phase to the other, 874.4 kcalmol-1 must be given to the system to counteract the natural change in entropy. This situation does not occur in GC but is conceivably possible in LC. (f) is the incremental increase in entropy for unit increase in enthalpy.

 

The standard enthalpy can be related to certain physical properties of the elements concerned. The conditions of measurement determine that the interactions are solely dispersive. As a first approximation, the interaction energy involved with dispersive forces between like molecule has been shown to be (9) a function of the Molar Polarizability.

Now, the polarizability (ap)can be expressed by the function

                                            

 

where (e) is the dielectric constant of the material
and (nv) is the number of molecules per unit volume.