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Physics · Earth & cosmosNuclear binding energy

A bound nucleus has less rest mass than its separated nucleons.

ModelPhysics · Earth & cosmosExponential radioactive decay

A fixed decay probability per time gives a population timescale.

ModelPhysics · Earth & cosmosFission, fusion and reaction energy

Nuclear rearrangement can release or require energy.

ModelPhysicsScattering cross section

Normalize a scattering rate by incident flux.

ModelPhysicsStandard Model matter families

Quarks and leptons form three generations.

ModelPhysicsStandard Model interactions

Gauge fields mediate three interactions; the Higgs is a scalar sector.

ModelPhysicsInteraction-specific quantum-number balances

A balance rule must name the interaction where it applies.

ModelPhysics · ChemistryBloch states and electronic bands

A periodic crystal potential organizes energies by wavevector and band.

ModelPhysics · ChemistrySemiconductor electrons and holes

Band occupancy and doping control mobile carriers.

ModelPhysicsBose and Fermi thermal occupations

Indistinguishable particles have different equilibrium state populations.

ModelChemistryElectron screening and effective nuclear attraction

Other electrons modify the attraction experienced by an electron in an atom.

ModelChemistryMultielectron ground-state configurations

Orbital occupations connect atomic electronic structure with valence chemistry.

ModelChemistryLocalized bonds and resonance descriptions

Localized orbital overlap and resonance are complementary chemical descriptions.

ModelChemistryMolecular orbitals and bonding occupation

A molecular orbital description distributes electronic states across a molecule.

ModelChemistryIntermolecular interactions

Dispersion, dipole interactions and hydrogen bonding influence molecular materials.

ModelChemistryBonding classes of solids

Ionic, metallic, molecular and network solids organize common bonding patterns.

DefinitionChemistryPolymers and macromolecular architecture

Polymers are substances composed of macromolecules with recurring structural units.

DefinitionChemistryCoordination compounds and ligands

Ligand donor atoms surround a central metal in a coordination sphere.

DefinitionChemistryActivities and chemical potentials

Activity expresses composition relative to a specified thermodynamic standard state.

DefinitionChemistrypH and hydrogen-ion activity

pH is an activity-based quantity realized through measurement conventions.

DefinitionChemistryBuffers and finite buffering capacity

An acid–base pair can resist limited changes in solution pH.

ModelChemistrySolubility products and precipitation

An equilibrium product constrains dissolution of a specified solid phase.

ModelChemistryReference electrodes and redox potentials

Electrode potentials are specified relative to a reference half-cell.

DefinitionChemistryThe Nernst equilibrium relation

Reversible electrochemical potential depends on activities and temperature.

ModelChemistryElementary steps and reaction mechanisms

A mechanism proposes steps that account for an overall chemical transformation.

ModelChemistryArrhenius temperature dependence

Many rate constants follow an exponential temperature model over a limited range.

ApproximationChemistryHess's law and thermochemical accounting

Reaction enthalpies can be combined because enthalpy is a state function.

ModelChemistryPhase diagrams and coexistence

Phase diagrams describe equilibrium states under stated conditions.

ModelChemistryCalibration, standards and matrix effects

Quantitative analysis needs a validated relation between response and analyte amount.

MethodChemistryChromatographic retention and separation

Differential interactions with mobile and stationary phases separate mixture components.

Method
ModelSource checked

The Nernst equilibrium relation

Chemistry

Reversible electrochemical potential depends on activities and temperature.

Key knowledge

The Nernst equation relates a reversible cell potential to its standard potential, temperature and reaction quotient. It follows from the thermodynamic relations between reaction Gibbs energy and reversible electrical work; it does not include current-dependent voltage losses.

Values and equations

E = E° − (RT / nF) ln Q

E
reversible cell potential V
E°
standard cell potential at the same temperature V
R
molar gas constant J mol⁻¹ K⁻¹
T
absolute temperature K
n
electron-transfer number for the balanced reaction 1
F
Faraday constant C mol⁻¹
Q
dimensionless reaction quotient formed from activities 1

Conditions and scope

  • Use a balanced cell reaction with a nonzero positive electron-transfer number and a dimensionless activity quotient.
  • Apply at the specified temperature and reversible conditions; kinetic overpotential and resistance need additional models.
Sources · 1

References

Sources retain their recorded scope. A source link alone does not establish verification of every statement.

  1. Chemistry 2e, 17.4: Potential, Free Energy, and EquilibriumPaul Flowers, Klaus Theopold, Richard Langley and William R. Robinson — OpenStax, Rice UniversityTextbook chapteropenstax.orgRead source

Evidence and review

Source derivation from Gibbs energy and reversible work.

2026-10-10 · Checked sign, activities and reversible-cell boundary.

Related reference entries

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Showing 1–6 of 6 relationships

Scientific relationships · 6 / 6

The relationship type describes the connection. Its linked statements, sources and conditions define the scope.

  1. Related to
    Relationship sources · 1

    Linked statements

    • The Nernst equation relates a reversible cell potential to its standard potential, temperature and reaction quotient. It follows from the thermodynamic relations between reaction Gibbs energy and reversible electrical work; it does not include current-dependent voltage losses.

    Reaction conditions modify a reversible cell's standard potential.

  2. Related to
    Relationship sources · 1

    Linked statements

    • The Nernst equation relates a reversible cell potential to its standard potential, temperature and reaction quotient. It follows from the thermodynamic relations between reaction Gibbs energy and reversible electrical work; it does not include current-dependent voltage losses.

    Reversible cell potential is related to reaction Gibbs energy.

  3. Related to
    Relationship sources · 1

    Linked statements

    • An ion's equilibrium potential balances its chemical and electrical driving terms. With multiple permeant ions, membrane voltage need not equal any one equilibrium potential. A conductance model separates ionic currents from capacitive charging.

    Electrochemical equilibrium is applied to one permeant ion.

  4. Related to
    Relationship sources · 1

    Linked statements

    • Potentiometry measures the potential difference between an analyte-responsive indicator electrode and a reference electrode with negligible measurement current. Equilibrium response depends on activity. Ion-selective membranes and redox electrodes require their own response/selectivity models and calibration.

    Equilibrium redox response uses the activity-based Nernst relation.

  5. Related to
    Relationship sources · 1

    Linked statements

    • Voltammetry records current while controlling the working-electrode potential relative to a reference; a counter electrode carries the balancing current. Faradaic response depends on redox kinetics and transport by diffusion, migration and convection. Double-layer charging and residual currents can add signals, so peak shape or current is interpreted with the actual waveform, geometry and calibration.

    Equilibrium potentials provide one limiting comparison.

  6. Related to
    Relationship sources · 1

    Linked statements

    • For a balanced redox reaction transferring n electrons per reaction event, the molar reaction Gibbs energy is ΔrG=−nFE at the same temperature and composition when E is its reversible cell potential. Thus ΔrG°=−nFE° and ln K=nFE°/(RT) under consistent dimensionless activity and standard-state conventions. Multiplying the balanced reaction multiplies n and ΔrG but does not multiply E.

    The activity quotient relates reversible E to its standard value.

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chem-nernst-equation
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