Variation of reactant ratio for second-order reaction A+B->products,M=CBo/CAo (3.13) 一rA=-rB=KCACB behave as second-order reactions of one component when the reactant ratio is unity.Thus -rA=kCACB=kC when M=1 (3) On the other hand,when a large excess of reactant B is used then its concentration does not change appreciably(Ca=CBo)and the reaction approaches first-order behavior with respect to the limiting component A,or -rA kCACB =(kCBO)CA =k'CA when M>1 (4) Thus in Fig.6.1,and in terms of the limiting component A,the size ratio of mixed to plug flow reactors is represented by the region between the first-order and the second-order curves.9 • Variation of reactant ratio for second-order reaction