according to the equation, For families of reactions, the Polanyi-Semenov equation can be used to estimate activation energies from the heats of reaction, according to the equation,
E = C - 
()
where and C are constants. For expthermic reactions, = -0.25 and C = 48 kJ/mol, while for endothermic reactions, = -0.75 and C = 48kJ/mol. However, these values may vary somewhat from reaction family to reaction family [K.J. Laidler, Theories of Chemical Reaction Rates (New York, R. E. Krieger, 1979), p. 38]. (Also see Appendix J)
(a)Why is this a reasonable correlation?
Consider the following family of reactions:
(b)Estimate the activation energy for the reaction
which has an exothermic heat of reaction of 6 kcal/mol (i.e., = -6 kcal/mol)