Reacciones complejas: relojes químicos

Abstract

Clock reactions represent a complex group of non-standard kinetic processes that hold significant importance in biological systems. These reactions are characterized by a sudden change in the concentration of one of the reacting species, accompanied by a visible or easily measurable property variation. In this study, a Landolt-type clock reaction was analyzed, featuring a sharp color change after a specific induction period. The reaction investigated involves sodium bisulfite and potassium iodate in the presence of starch, which serves as an indicator.

To explore this system, two sets of experiments were carried out. In the first series, the initial concentration of potassium iodate was varied while keeping the sodium bisulfite concentration constant. In the second series, the reaction temperature was systematically altered while maintaining the same initial reactant concentrations. The aim of these experiments was to determine how the induction period depends on potassium iodate concentration and temperature.

The results demonstrated that lowering the potassium iodate concentration increases the induction time because the rate of triiodide ion formation decreases, delaying the depletion of sodium bisulfite. Conversely, increasing the temperature reduced the induction period, a behavior consistent with the Arrhenius model, which also allowed for the calculation of the activation energy of the overall process.