89.6 Rate Theories of elementary reaction 9.6.2 Calculation of ZaB When the concentration of a is Na/v(molec.m AB Abv v When both A and B moves, the relative velocity uaR Should be used AB D+UWhen the concentration of A is NA /V (molecm-3 ): 2 AB AB Z =d V N V NA B  A When both A and B moves, the relative velocity AB should be used. ( ) 2 2  AB =  A + B 9.6.2 Calculation of ZAB §9.6 Rate Theories of elementary reaction