Physical Chemistry 3: — Chemical Kinetics — - Christian-Albrechts ...

11.5 Reactions of ions in solutions 239
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Dependence of the rate constant on the ionic strength:
³
´
log =log 0 − 2 + 2 − ‡ 2
12
(11.62)
with ‡ = + .
Inserting ‡ = + ,weobtain
log =log 0 − ¡ 2 + 2 − ( + ) 2¢ 12
(11.63)
y
log 0
=+2 12
(11.64)
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Conclusions:
• If and havethesamesign,then will increase with increasing , because
the repulsion is reduced by the shielding effect of the ion cloud.
• If and have opposite sign, then will decrease with increasing , because
the attraction is reduced by the shielding effect of the ion cloud.
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Figure 11.8: Kinetic salt effect for reactions of ions in solution.