Theory of kinetic salt effects in diffusion-controlled reactions. Part 1.—Reactions between ions with equilibrium ion atmospheres

Abstract

The theory of Debye, based on Smoluchowski's expression for the encounter number, has been extended in order to calculate kinetic salt effects for diffusion-controlled reactions between ions. The dependence of the computed rate constants on ionic strength is found, in general, to be less than predicted by the Brønsted-Bjerrum equation, but there is little discrepancy at very low ionic strength. The effects of variable and unlike size of the reacting ions are slight. The substitution of more reasonable boundary conditions for those of Smoluchowski has little effect on the dependence of rates on ionic strength, but the calculated rate becomes less. These and other considerations make doubtful the assertions that certain reactions of the hydrated electron are not sufficiently fast to be diffusion controlled.