The Thermodynamics of Chromatography - Interactions Between the Atoms of Hydrogen, Carbon, Chlorine and Bromine and an Exclusively Dispersive Stationary Phase > Experimental Data > Page 36

Figure 13.Graphs of DH' for Each Element against the Reciprocal of the Absolute Temperature




The numerical results are summarized in Table 3. A value of 1.987 kcalK˚-1mol-1 was taken as the value for (R) and was used to calculate the values of (DHo) and (DSo) for each element which are also included in table 3. It is seen from equation (23) and the results shown in table 3 that (DHo) and (DSo) for each element are both negative. A negative value for (DSo) means that the entropy is reduced when the atom moves into the environment of the stationary phase from the gas phase and the atoms are more organized and less random.


Table 3 Standard Enthalpies and Entropies for the Elements Hydrogen, Carbon, Chlorine and Bromine


Element    Slope  DHo/2.303R  Intercept   DSo/2.303R     DHo   kcalmol-1     DSo kcal˚K-1mol-1
Hydrogen 169.8 -0.3705 -777 -1.695
Carbon 228.9 -0.4387 -1047 -2.007
Chlorine 349.6 -0.5588 -1600 -2.557
Bromine 531.4 -0.7460 -2432 -3.413