Dynamic equilibrium is one of the most important concepts in IB Chemistry. You’ll encounter it in reversible reactions, Le Chatelier’s Principle, equilibrium constants, acids and bases, and even electrochemistry. Because it forms the foundation of multiple topics, examiners expect you not only to define it correctly but also to explain its behavior in molecular terms.
If you're solidifying your understanding of core IB terminology, you may also find The Importance of Understanding Command Terms in IB Exams helpful for writing accurate, high-scoring explanations.
Quick Start Checklist
Before diving in, make sure you understand:
- Dynamic equilibrium occurs in a closed system.
- The forward and reverse reactions occur at the same rate.
- Concentrations of reactants and products remain constant, not equal.
- Particles are continuously reacting.
- The system is stable but still active on the particle level.
These points appear frequently in Paper 2 questions, especially in “explain,” “distinguish,” or “state” prompts.
What Is Dynamic Equilibrium?
Dynamic equilibrium describes a state in a reversible reaction where the forward and reverse reactions occur at the same rate, so the concentrations of all reactants and products remain constant over time.
The word “dynamic” is essential. It means:
- Reaction particles continue reacting.
- Products are still turning back into reactants.
- There is continuous molecular activity.
However, because the rates are equal, there is no net change in concentration.
A familiar example is:
N₂(g) + 3H₂(g) ⇌ 2NH₃(g)
At equilibrium, nitrogen and hydrogen still form ammonia, and ammonia still decomposes—but the overall amounts don’t change.
