Equilibrium relationships for non-equilibrium chemical dependencies

TL;DR

This paper demonstrates that equilibrium constants govern the time-dependent ratios of concentrations in reversible first-order reactions, revealing certain ratios remain constant over time in various reactor types.

Contribution

It introduces the concept of time invariants in chemical kinetics, showing equilibrium constants determine specific concentration ratios at all times in different reactor systems.

Findings

Certain concentration ratios equal equilibrium constants at all times.

Time invariants exist for reversible first-order reactions.

Relationships hold for both batch and steady-state plug-flow reactors.

Abstract

In contrast to common opinion, it is shown that equilibrium constants determine the time-dependent behavior of particular ratios of concentrations for any system of reversible first-order reactions. Indeed, some special ratios actually coincide with the equilibrium constant at any moment in time. This is established for batch reactors, and similar relations hold for steady-state plug-flow reactors, replacing astronomic time by residence time. Such relationships can be termed time invariants of chemical kinetics.