94.
The kinetics of oxidation of thiosulfate to tetrathionate by
trans-dihydroxotetraoxoosmate(VIII) in aqueous alkaline media have been studied. The oxidation follows a rate expression where
KOs is the formation constant of
trans-dihydroxotetraoxoosmate (VIII), and
K2 and
k3, respectively, represent the formation constants of the intermediate complex involving Os(VIII) and S
2O and its decomposition constant. The
KOs,
K2, and
k3 values have been computed to be (19.5 ± 3) dm
3/mol, (6.12 ± 0.5) and (3.32 ± 0.3) × 10
?1 dm
3/mol s at 303 K, and
I = 0.32 mol/dm
3, respectively. The rate law is consistent with a mechanism envisaging the equilibrium formation of an intermediate complex involving Os(VIII) and S
2O, followed by a rate-determining decomposition of the complex with concomitant electron transfer.
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