Свободные колебания при протекании гомофазных реакций

Abstract

Выявлены закономерности колебательного протекания гомогенных и гетерогенных гомофазных реакций. Определены условия свободных колебаний концентрации и температуры в закрытой гомогенной реакционной системе. Дано аналитическое описание закономерностей образования структур Лизеганга.

Homogeneous and heterogeneous homophase reactions in their wave regimes are studied. Conditions for arising free concentrational oscillations in a closed homogeneous reaction system are determined. Quantitative description for the wave regime of a heterogeneous homophase reaction is given with special attention to forming Liesegang patterns. In an oscillating chemical reaction, the concentrations of some components of the reaction mixture pass repeatedly through the same value, but the reaction proceeds continuously toward completion. Thermodynamical mechanism of such reactions is revealed, along with the phenomenology that these reactional systems exhibit, from single-frequency chemical oscillations to concentrational waves and Liesegang patterns. Special attention is paid to the fact that chemical oscillations arise not only due to positive or negative feedback. The oscillations in a reaction are driven by the decrease in free energy of the reaction mixture, and this decrease is the driving factor of all chemical reactions, but not all chemical reactions exhibit oscillations. Chemical oscillations have at least three common features. First, the reaction mixture is far from stable equilibrium. Second, the reaction is to be able to follow two different pathways. Third, one of these pathways produces a certain intermediate, while another pathway consumes it, and the concentration of this intermediate acts as a trigger that switches the reaction repeatedly from one pathway to the other.