Equilibrium is Dynamic
Chemical equilibrium is not a standstill — it is a dynamic balance where forward and reverse reactions proceed at identical rates. Reactant molecules continuously transform into products, and products continuously revert to reactants, but the net effect is zero change in concentrations. This simulation shows both rates as animated flows, making the dynamic nature of equilibrium tangible.
The Kinetic Origin of Keq
The equilibrium constant Keq = kf/kr emerges naturally from the condition that forward and reverse rates are equal: kf[A]eq = kr[B]eq gives [B]eq/[A]eq = kf/kr. This profound connection between kinetics and thermodynamics shows that equilibrium composition is determined by the relative speeds of competing reactions, not by any static energetic preference.
Le Chatelier in Action
When you add extra reactant (positive perturbation), the forward rate temporarily exceeds the reverse rate, converting the excess toward product until a new equilibrium is established. The system 'resists' the perturbation by partially consuming what was added. This principle, formulated by Henri Louis Le Chatelier in 1884, is one of the most useful qualitative predictions in chemistry.
Approach to Equilibrium
Starting from pure reactant, the approach to equilibrium is exponential with a time constant τ = 1/(kf + kr). The visualization plots concentrations of A and B over time, clearly showing the exponential approach and the final equilibrium values. The perturbation slider lets you disturb the equilibrium and watch the system relax to its new balance — Le Chatelier's principle made visual.