In this paper the expression for adsorption isotherm expressed by an asymptotic development, the extended Freundlich's isotherm, was applied to the study and interpretation of energetic heterogeneity. This expression presents the relative monolayer coverage of the entire surface as a dependence on adsorbate pressure (or concentration) and on parameters m and b(0), which were identified with the Freundlich's parameters. The value of m and b(0) were obtained by adjusting the cited expression to the experimental data for hydrogen adsorption on tungsten. The rn parameter shows a quadratic dependence on temperature. Our analysis shows that N(Q) the exponential form for the continuous energy distribution, is very dependent on m. A representative parameter is the dispersion of N(Q), delta = RT/m. We interpret the dependence of N(Q) on m as an indication of the energetic heterogeneity of this system. The parameter b(0) was adjusted by a van't Hoff expression, indicating a thermal process on the Langmuir adsorption sites.