G vacancy anion of MG

This reaction starts from the weakly adsorbed G gas and the vacancies of G in MG. It refers to the reverse of reaction [2.R.9]. It also involves two junq)s and therefore two elementary steps. 

The voluminal speed of this elementary step can be written as (defects being diluted)  

The two preceding steps consider an equivalent reaction (see section 7.9) that can be written as  

The voluminal speed of this reaction can be expressed in the form  

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