Not a Fact Anymore
DE

Not a fact anymore

At chemical equilibrium, the forward and reverse reactions have stopped.

What we know now

Chemical equilibrium is dynamic. Forward and reverse processes continue at equal rates, leaving concentrations and other macroscopic properties approximately constant.

Why it changed

Equilibrium mixtures appear unchanged, and early static interpretations treated that constancy as cessation. Kinetic theory, isotope tracing, and rate measurements showed continuing molecular exchange in both directions.

Status
Overturned
Category
Chemistry
Accepted for
≈14 years
Accepted approximately
19th century–early 20th century
Changed approximately
Late 19th–20th century

Equal rates do not imply equal concentrations. An equilibrium can strongly favor reactants or products while both reactions continue.

A system that merely changes too slowly to observe is not necessarily at equilibrium, and a steady state maintained by continuous inputs and outputs is a different condition.

Evidence

Sources and what they establish

Current evidence

  • The Dynamic Nature of EquilibriaChemistry LibreTexts

    Explains that forward and reverse reactions continue at equal rates at equilibrium.

  • Chemical equilibriumInternational Union of Pure and Applied Chemistry

    Provides the modern thermodynamic definition of chemical equilibrium.

Historical context

  • Studies in Chemical DynamicsFrederick Muller

    Van 't Hoff's work helped establish a kinetic understanding of reversible reactions and equilibrium.

Related entries

Chemistry

Fermentation requires intact living cells and cannot occur in a cell-free extract.1897 · OverturnedStable organic free radicals cannot be isolated.1900 · Overturned
Browse Chemistry →

Around 1864

Electricity and magnetism are fundamentally separate forces.1865 · PhysicsLiving organisms were generally expected to require a continuous supply of free oxygen to survive and grow.1861 · Biology
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