A reversible reaction can proceed in both the forward and reverse directions. At dynamic equilibrium, the rates of the forward and reverse reactions are equal — but both reactions are still occurring.
Conditions for Dynamic Equilibrium
- The system must be closed (no substances enter or leave)
- Rate of forward reaction = rate of reverse reaction
- Macroscopic properties (concentrations, colour, pressure) remain constant
- At the molecular level, both reactions continue
Reaching Equilibrium
Concentrations become constant when equilibrium is reached — but the reactions have not stopped.
Think About It
If you open a bottle of fizzy water, is the CO₂(aq) ⇌ CO₂(g) system at equilibrium?
No — the system is no longer closed. CO₂ gas escapes, so the forward reaction is favoured and the position shifts to the right until all dissolved CO₂ has escaped.