Dynamic Equilibrium
Definition and meaning of Dynamic Equilibrium in chemistry.
Dynamic equilibrium is the state of a reversible reaction in a closed system in which the forward and reverse reactions proceed at equal rates, so the macroscopic concentrations of reactants and products remain constant over time.
In more detail
Although concentrations appear fixed, molecules continue reacting in both directions at the same rate, so the system is balanced rather than stopped. This state is only reachable in a closed system, since matter entering or leaving would prevent the forward and reverse rates from staying matched. The position of a dynamic equilibrium is described quantitatively by the equilibrium constant, K, and Le Chatelier's principle predicts how that position shifts when concentration, pressure, or temperature is changed.
Key facts
| Field | Physical Chemistry |
|---|---|
| Requires | Closed system |
| Condition | Rate(forward) = Rate(reverse) |
| Governed by | Equilibrium constant, K |
In a sealed flask, N2O4(g) ⇌ 2NO2(g) reaches dynamic equilibrium when colorless N2O4 decomposes into brown NO2 at the same rate that NO2 recombines into N2O4, producing a constant brownish color even though both reactions keep occurring.
Frequently asked questions
Does dynamic equilibrium mean the reactions have stopped?
No. Both the forward and reverse reactions continue indefinitely; equilibrium means there is no net change in concentration, not that reaction has ceased.
Why must dynamic equilibrium occur in a closed system?
A closed system prevents matter from entering or leaving, so the total amount of each substance stays fixed, allowing the forward and reverse rates to settle into balance.