Zoltán Köntös
The thermal decomposition of hydrogen peroxide (H₂O₂) is a reaction of profound fundamental and industrial significance, serving as a model system for understanding reaction kinetics and as a critical process in chemical, environmental, and biomedical engineering. This study aimed to experimentally determine the reaction rate constants for the uncatalyzed decomposition of H₂O₂ in aqueous solution and to calculate the associated Arrhenius parameters (activation energy, E a , and pre-exponential factor, A ). The decomposition was monitored via permanganometric titration, allowing for the direct quantification of H₂O₂ concentration over time in the absence of any added catalyst. Experiments were conducted at controlled temperature. The reaction progress was tracked, and the data were treated assuming first-order kinetics with respect to H₂O₂ concentration. The rate constants ( k ) were determined from the linear regression of ln[H₂O₂] versus time plots. The Arrhenius plot (ln k vs 1/ T ) yielded an excellent linear fit (R² > 0.99), from which the activation energy was calculated to be 55.3 ± 1.8 kJ mol⁻¹, and the pre-exponential factor was 1.86 ∙ 10¹⁰ h⁻¹. These values are consistent with the higher energy barrier expected for uncatalyzed homolytic O-O bond cleavage. Furthermore, the study quantified the pronounced stabilizing effect of boric acid, which reduced the decomposition rate constant by approximately 80% through the formation of a stable peroxo-borate complex. The methodology and findings provide a robust framework for teaching advanced kinetic concepts and have direct implications for optimizing the storage, stability, and safe handling of H₂O₂ in industrial processes and consumer products. This work uniquely bridges uncatalyzed kinetics with practical stabilization, offering predictive models absent in literature.