Desorption—readsorption mechanism

The ratio of the coverages determines the ratio of trans and cis dialkylcyclohexanes. It follows then, that in general the cis to trans ratio for the desorption-readsorption mechanism versus the rollover mechanism have different dependencies on the concentrations of the reactants. However, if the frequencies of steps 1-4 are very high (desoprtion and readsorption are equilibrated) analysis of eq.(4.105) leads to... 

It was found that chemisorption equilibrium is rapidly attained in most reacting systems through rapid desorption and readsorption. With a few exceptions, chemisorbed molecules can be regarded as immobile since statistical-mechanical calculations of the chemisorption equilibrium agree well with the experiment if two-dimensional translations and rotations of the chemisorbed molecules are assumed to be nonexistent. The chemisorbed state of di- or triatomic molecules can be molecular or atomic, depending on the nature of the adsorbent. For example, the carbon dioxide molecule is chemisorbed with complete dissociation into its three atoms on metallic surfaces, while on oxidic catalysts it is chemisorbed with only partial dissociation. 

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