At equilibrium, opposing reactions continue without net composition change.
Key knowledge
In a reversible reaction at chemical equilibrium, the forward and reverse reaction rates are equal. Reactant and product concentrations remain constant under unchanged conditions, although reactions continue in both directions.
Conditions and scope
Describes a closed reaction system under fixed conditions, not an externally driven steady state.
Equal rates do not imply equal reactant and product concentrations.
Sources · 2
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Published dynamic-equilibrium account and sealed-system examples; no equilibrium measurement was repeated.
2026-10-10 · English rate/composition distinction checked against Chemical Equilibria; detailed multi-reaction kinetics are outside scope.
Foundational review
2026-10-10 · Fresh primary-source inspection of the complete compact record, including every statement, equation, quantity and material condition, followed by independent AI editorial review. This check does not certify all linked lessons or every passage of every cited publication.
Sources from other places
Agreement within this scope
Equal forward/reverse rates with unchanged bulk concentrations.
In a reversible reaction at chemical equilibrium, the forward and reverse reaction rates are equal. Reactant and product concentrations remain constant under unchanged conditions, although reactions continue in both directions.
Gibbs energy is G = H − TS. At constant temperature and pressure, a process in a closed system with only pressure-volume work is thermodynamically favoured when its Gibbs-energy change is negative. This criterion does not specify how quickly the process proceeds.
Equilibrium and Gibbs-energy criteria are connected under the specified thermodynamic constraints.
A catalyst provides an alternative reaction pathway that increases the rate and is regenerated in the overall reaction. Catalysed pathways can have lower activation barriers. For the same reversible reaction under fixed thermodynamic conditions, catalysis can hasten the approach to equilibrium without changing its equilibrium constant.
In a reversible reaction at chemical equilibrium, the forward and reverse reaction rates are equal. Reactant and product concentrations remain constant under unchanged conditions, although reactions continue in both directions.
Catalysis accelerates approach to equilibrium for the same reaction without changing its equilibrium constant.
For a specified dissolution reaction, a solubility product relates equilibrium ion activities; a pure solid's activity is conventionally one. Comparing the reaction quotient with the equilibrium value indicates a thermodynamic tendency toward dissolution or precipitation.
Ksp describes a specified dissolution equilibrium.
For a balanced reaction with signed stoichiometric coefficients νᵢ, the reaction quotient is the product of activities raised to those coefficients. At equilibrium Q equals the dimensionless equilibrium constant K for the specified temperature and standard states.
Q=K identifies the specified equilibrium composition.
Solubility specifies an equilibrium dissolved composition for a solute, solvent and relevant phase at stated conditions. Relative to that limit, an unsaturated solution contains less solute, a saturated solution is at the limit, and a supersaturated solution contains more and is outside stable equilibrium with the relevant solute phase. Supersaturation can persist until nucleation or another pathway permits separation. A concentrated solution can be unsaturated, and a dilute solution can be saturated.
Solubility refers to equilibrium with a specified phase; supersaturation is outside that stable equilibrium.