Langmuirs equation for monolayer adsorption

From kinetic theory, the number of molec es striking unit area in unit time is given by  

If the fraction of the surface covered with adsorbed molecules at pressure F is d then the rate of adsorption on an area (1-0 ) equals the late of desorption from an area (0). 

A plot of PtV against P (or xtV against x) yields the monolayer capacity Vffi and to relate this to surface area it is necessary to know the area occupied by one molecule, a. 

Surface area is calculated from monolayer capacity using the following relationship  

Hence for nitrogen at liquid nitrogen temperature 023x1023)06.2x10-20) 

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