Beginner Topic 463 of 1102 Kinetics & Equilibrium
Dynamic Equilibrium
The state in which forward and reverse reaction rates are equal and concentrations remain constant.
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In-depth explanation of Dynamic Equilibrium
Dynamic equilibrium is the state in which the forward and reverse reaction rates are equal, so the concentrations of all species remain constant over time. Although the macroscopic composition no longer changes, molecules continue to react in both directions at equal rates, which makes the equilibrium dynamic rather than static. The state can be approached from either the reactant or the product side, and it is reached in a closed system after sufficient time. Isotope labelling experiments demonstrate this dynamic nature, because labelled atoms are found to exchange between species even though their concentrations do not change.
Going deeper: Dynamic Equilibrium
Key ideas: At equilibrium rate forward = rate reverse, each nonzero, so molecular exchange continues. Equilibrium can be reached from either side and the final composition is the same given the same total amounts and temperature. Equilibrium needs a closed system; in an open system, concentrations may be steady but not at equilibrium.
Common mistakes and connections: Students believe that at equilibrium concentrations are equal or that reaction has stopped. Concentrations are constant, not necessarily equal, and in a ratio set by K. Another mistake is thinking that adding a catalyst changes the amounts present. It only shortens the time to reach equilibrium. Compare with steady state, where net flux continues. Related to the reaction quotient and Le Chatelier.
Visualization of Dynamic Equilibrium
At equilibrium particles keep converting both ways at equal rates, so the overall composition stays constant even though molecules keep reacting. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Water molecules containing oxygen-18 placed in contact with ice at 0 degrees C slowly exchange into the solid, showing that molecules keep moving in both directions.
Frequently asked questions about Dynamic Equilibrium
What is Dynamic Equilibrium?
The state in which forward and reverse reaction rates are equal and concentrations remain constant.
Is Dynamic Equilibrium a beginner, intermediate or advanced topic?
Dynamic Equilibrium is a beginner topic in Kinetics & Equilibrium. It needs no earlier chemistry lessons and is a good starting point.
What should I learn before Dynamic Equilibrium?
Study these earlier topics in Kinetics & Equilibrium first: Photochemical Reactions, Quantum Yield, Reversible Reactions.
What comes after Dynamic Equilibrium?
The next topics in Kinetics & Equilibrium are Equilibrium Constant and Kc and Kp.
Can I practise Dynamic Equilibrium with quizzes?
Yes. The interactive lesson includes a self-check question on Dynamic Equilibrium, and the Kinetics & Equilibrium quiz draws on every topic in this area.
Where Dynamic Equilibrium fits in Kinetics & Equilibrium
Dynamic Equilibrium is topic 44 of 91 in Kinetics & Equilibrium.