Decomposition of hexaaquacobalt(III) in perchloric acid

The reaction of View the MathML sourceCo(OH2)63+ with water has been studied in 1.0 M HClO4/LiClO4 at 25 °C. The reaction is biphasic, showing an initial increase and then decrease in absorbance at 325 and 605 nm. The rate of increase depends on View the MathML source[Co(OH2)63+]2and [H+]−2, while the decrease has an [H+]−1 dependence. The [H+]−2 and [H+]−1 dependence for the absorbance increase and decrease, respectively, may be accounted for by hydrolysis equilibria of View the MathML sourceCo(OH2)63+ and oligomeric species. The calculated values for k 1K 1 and k 2K 2 that fit the data are 3.5 × 10−3 s−1 and 3.2 × 10−3 M s−1, respectively, where K 1 is the hydrolysis constant of View the MathML sourceCo(OH2)63+, k1 is the rate for the absorbance increase, K2 represent the hydrolysis constant for the oligomer and k2 the rate constants for the absorbance decrease.