89.5 Arrhenius equation 9.5.8 Theoretical evaluation ofe 2)Combination reaction of radicals The activation energy can be related to the energy change of the reaction. The energy 2CH3→>CH3-CH change can be calculated using dissociation E.=0 energy of chemical bond. (NOT BOND ENERGY. To do this, some empirical rules may be used 3)Radicals react with molecules: A·+B-C→A-B+C 1)Dissociation reaction: Cl-Cl→2Cl If the reaction is a exothermal one, Eas5% DB-c5 Ea will not be less than and need not be 4) Molecules react with molecules larger than the dissociation energy of the A-B+C-D→A-C+B-D bond, i.e., Ea=Dcl-ci If the reaction is exothermal, Ea=30% (Dab D9.5.8 Theoretical evaluation of Ea : The activation energy can be related to the energy change of the reaction. The energy change can be calculated using dissociation energy of chemical bond. (NOT BOND ENERGY). To do this, some empirical rules may be used: 1) Dissociation reaction: Ea will not be less than and need not be larger than the dissociation energy of the bond, i.e., Ea = DCl-Cl Cl−Cl → 2 Cl §9.5 Arrhenius equation 2) Combination reaction of radicals 2CH3· → CH3−CH3 Ea = 0 3) Radicals react with molecules: A + B−C → A−B + C If the reaction is a exothermal one, Ea  5% DB-C ; 4) Molecules react with molecules: A−B + C−D → A−C + B−D If the reaction is exothermal, Ea = 30% (DAB + DCD)