https://doi.org/10.1351/goldbook.C01191
A reduction in the
This phenomenon is a direct consequence of the
rate
of certain reactions of a substrate
RX in solution [by a path that involves a pre-equilibrium
with formation of R+ (or R− ) ions as reaction intermediates] caused by the addition to the reaction mixture of an electrolyte solute containing the 'common ion' X− (or X+). For example, the rate of solvolysis
of diphenylmethyl chloride in acetone-water is reduced by the addition of salts of the common ion Cl- which causes a decrease in the quasi-equilibrium
concentration of the diphenylmethyl cation
in the scheme: ![Not defined](/img/inline/C01191-1.png)
![Not defined](/img/inline/C01191-2.png)
mass-law effect
on ionization
equilibria in electrolytic solution. More generally, the common-ion effect is the influence of the 'common ion' on the reactivity due to the shift of the dissociation
equilibrium. It may also lead to an enhancement of the rate
.