General laws of solid state reaction

The most common character of chemical reaction is the quantitative changes of substance at unit volume and time. 

v is the instantaneous rate of chemical reaction, N is the molar number of substance, V is the volume, t is the time. 

Because N/V = c is molar concentration of substance, when the reaction volume is a constant, the reaction rate can be expressed as  

According to mass action law of the chemical kinetics, the reaction rate of yiA + 

Solid state chemical reaction involves local reactions. As at least one of the reactant and product is solid, the reaction does not occur in the bulk of substance, but on the interface of phase boundary. Therefore the above expression as chemical reaction rate cannot be used for local reactions. In local reactions, the reaction rate should be interpreted as changes of the conversion of substance with time. 

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