ABSTRACT

The spectrophotometric method monitored the uncatalysed redox reaction between Mn⁺⁷/H⁺ ions and mannose sugar molecules kinetically at constant ionic strength maintained using potassium nitrate (KNO₃). The kinetic study showed that the reaction was pseudo-first order concerning Mn⁺⁷ and mannose, and the rate of reaction increases by increasing the concentration of Mn⁺⁷, mannose and H⁺ and increasing temperature. The reaction rate was enhanced by 3 × 10^–4m of Mn⁺⁷ concentration, and the oxidation with Mn⁺⁷ was faster using 2 × 10^–2m of mannose and 5 × 10^–1m of H⁺. The temperature dependence was carried out under fixed experimental conditions, from which the activation energy of the reaction (E_a) in KJ.mol^–1 was found to be 61.1, and the frequency factor (A) in sec^–1 was 10.52 × 10⁵ other physical functions, namely, the free energy change (∆G) in KJ.mol^–1 and the entropy change (∆S) in J.K ^–1 were also calculated at different temperatures. Qualitative analysis of the reaction products revealed the formation of formic acid. A rate law was derived from the proposed mechanism, which agreed well with experimental kinetics.

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