Physical Concept of Site Heterogeneity

From a physical viewpoint, since the Elovich equation has been found to be obeyed for adsorption rates on finely divided powders and on metal films, one might consider the total surface to comprise a small number of different crystal faces for which the activation energy for adsorption (and desorption) and their area would differ. Owing to the imperfect nature of real crystal planes, these will not have a set of completely uniform sites but such imperfections will not affect the following considerations about the minimum number of different sets of sites required so that the Elovich equation describes the adsorption rate 

The summation cannot be effected analytically, so the rate has been numerically computed. 

Aj 23 1-2 kcal. It is evident that the result of any departures from the 

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