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Showing 841–870 of 1709 reference entries

Earth & cosmosFolds, faults and relative displacement

Fold geometry includes limbs, hinge/axis and axial surface; antiform/synform describe shape while anticline/syncline also depend on stratigraphic order.

DefinitionEarth & cosmosStrike, dip and geological map constraints

Strike is the bearing of a horizontal line in a plane; dip is the maximum inclination from horizontal, perpendicular to strike, with direction specified.

MethodEarth & cosmosRelative dating and unconformities

Superposition constrains age order in an undisturbed depositional sequence; inclusions predate their host, and cross-cutting features postdate what they cut.

MethodEarth & cosmos · BiologyFossils, correlation and palaeoenvironment

Fossil assemblages can constrain relative age and depositional environment through observed succession and known ecological context.

MethodEarth & cosmosSedimentary facies and basin interpretation

Grain size, sorting, sedimentary structures, composition and fossils together constrain depositional processes and environments.

ModelEarth & cosmosIsostasy and load response

Isostasy describes buoyancy-related balance of lithospheric columns over a deformable mantle in an appropriate model.

ModelEarth & cosmos · ChemistrySilicate structures and substitution

Silicate structures organize silicon–oxygen tetrahedra as isolated units, chains, sheets or frameworks.

DefinitionEarth & cosmosPartial melting and magma formation

Rock can begin melting without every component entering the liquid.

ModelEarth & cosmosCrystallization and igneous differentiation

Crystallizing minerals remove selected chemical components from a melt.

ModelEarth & cosmos · ChemistryMetamorphic assemblages and phase constraints

Metamorphism changes mineral assemblage and texture under changed pressure, temperature, fluid and deformation conditions without requiring bulk melting.

ModelEarth & cosmos · Chemistry · BiologyWeathering, soil formation and chemical export

Mechanical weathering changes fragment size; chemical weathering transforms or dissolves minerals through reactions such as hydrolysis and oxidation.

ModelEarth & cosmos · ChemistryGeochemical partition coefficients

A distribution coefficient relates one species' concentrations in two specified coexisting phases.

ModelEarth & cosmos · ChemistryBatch melting and fractional crystallization models

In homogeneous constant-D batch melting, mass balance and equilibrium give melt enrichment Cℓ/C₀=1/[D+F(1−D)].

ModelEarth & cosmosSediment entrainment, transport and deposition

Streams carry bed load, suspended material and dissolved solutes through different processes.

ModelEarth & cosmosAquifer storage, permeability and recharge

Porosity measures pore-space fraction, while hydraulic permeability/conductivity concerns connected flow under stated fluid conditions.

ModelEarth & cosmos · ChemistryGroundwater chemistry and transport context

Groundwater exchanges dissolved species with aquifer minerals and surfaces.

ModelEarth & cosmosGlacier mass balance and ice motion

Glacier accumulation and ablation determine a mass budget; an equilibrium line separates zones in the specified surface-balance picture.

ModelEarth & cosmosGlacial erosion and depositional evidence

Moving ice can abrade and pluck bedrock, while transported debris can be deposited directly as till or sorted by meltwater.

ModelEarth & cosmosGlobal and relative sea-level change

Relative sea level is water level measured against local land.

ModelEarth & cosmosAtmospheric and oceanic hydrostatic balance

When vertical acceleration is negligible, the vertical pressure gradient balances gravity: ∂p/∂z=−ρg for upward z.

ApproximationEarth & cosmosGeostrophic flow and Rossby-number scope

For sufficiently slowly varying large-scale flow away from strong friction, horizontal pressure-gradient and Coriolis accelerations can approximately balance.

ApproximationEarth & cosmosDry adiabatic motion and potential temperature

For an ideal dry gas with constant heat capacities, potential temperature θ=T(p₀/p)^(Rd/cp) is conserved in reversible adiabatic parcel motion.

ModelEarth & cosmosHumidity, condensation and clouds

Water-vapour amount and relative humidity are distinct; relative humidity compares vapour pressure with a specified saturation value at the current temperature.

ModelEarth & cosmosOcean density, stratification and mixing

Seawater density depends on temperature, salinity and pressure.

ModelEarth & cosmosWind stress and Ekman transport

In the steady idealized surface Ekman layer, vertically integrated mass transport is ME=τ×ẑ/f.

ApproximationEarth & cosmosWind-driven gyres and vorticity constraints

Spatially varying wind stress can cause Ekman convergence/divergence and force interior ocean circulation.

ModelEarth & cosmos · Chemistry · BiologyMarine carbonate speciation and exchange

Dissolved inorganic carbon includes aqueous CO₂/carbonic-acid convention, bicarbonate and carbonate.

ModelEarth & cosmosPalaeoclimate proxy and chronology inference

Natural archives such as ice, sediments, corals and tree rings record properties related to past environments.

MethodChemistryReaction quotient and equilibrium constant

For a balanced reaction with signed stoichiometric coefficients νᵢ, the reaction quotient is the product of activities raised to those coefficients.

ModelChemistryReaction Gibbs energy and equilibrium

The molar Gibbs energy of a reaction at its current composition is ΔᵣG = ΔᵣG° + RT ln Q.

Model
ModelSource checked

Reaction Gibbs energy and equilibrium

Chemistry

The molar Gibbs energy of a reaction at its current composition is ΔᵣG = ΔᵣG° + RT ln Q.

Key knowledge

The molar Gibbs energy of a reaction at its current composition is ΔᵣG = ΔᵣG° + RT ln Q. At equilibrium it vanishes, giving ΔᵣG° = −RT ln K. The relation concerns thermodynamic direction and equilibrium, not reaction speed.

Values and equations

ΔᵣG = ΔᵣG° + RT ln Q; ΔᵣG° = −RT ln K

ΔᵣG
molar reaction Gibbs-energy change J mol⁻¹
ΔᵣG°
standard molar reaction Gibbs-energy change J mol⁻¹
R
molar gas constant J mol⁻¹ K⁻¹
T
absolute temperature K
Q
dimensionless reaction quotient 1
K
dimensionless equilibrium constant 1

Conditions and scope

  • Use the same balanced reaction, temperature and standard states in ΔᵣG°, Q and K.
  • The direction criterion assumes fixed temperature and pressure with the stated work constraints; concentrations alone may not equal activities.
Sources · 1

References

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

  1. Chemistry 2e, 16.4 Free EnergyPaul Flowers, Klaus Theopold, Richard Langley and William R. Robinson — OpenStax, Rice UniversityTextbook chapteropenstax.orgRead source

Evidence and review

Inspected the nonstandard Gibbs-energy expression and its equilibrium specialization.

2026-10-10 · Independent AI editorial review: All 94 actual compact claims, hypotheses, equation/variable/unit tables and 176 origin semantic links independently read. All exact author source-binding rows and disclosed extents assessed; targeted original bodies or specifically identified indexed primary passages rechecked below. All retained chemistry compact records read for combined breadth. Independent AI editorial content and practical common-core inventory review; no human specialist, degree/laboratory proficiency, whole-textbook certification or experimental replication. Receipt: chemistry-independent-content-inventory-review.1.

Related reference entries

Explore relationships within this area of study and its connections to other areas.

Showing 1–8 of 8 relationships

Scientific relationships · 8 / 8

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

  1. Uses definition
    Relationship sources · 1

    Linked statements

    • The molar Gibbs energy of a reaction at its current composition is ΔᵣG = ΔᵣG° + RT ln Q. At equilibrium it vanishes, giving ΔᵣG° = −RT ln K. The relation concerns thermodynamic direction and equilibrium, not reaction speed.

    The Gibbs relation uses the reaction activity quotient.

  2. Related to
    Relationship sources · 1

    Linked statements

    • The molar Gibbs energy of a reaction at its current composition is ΔᵣG = ΔᵣG° + RT ln Q. At equilibrium it vanishes, giving ΔᵣG° = −RT ln K. The relation concerns thermodynamic direction and equilibrium, not reaction speed.

    The reaction relation specializes Gibbs-energy accounting.

  3. Related to
    Relationship sources · 1

    Linked statements

    • Transition-state theory relates an elementary rate coefficient to a constrained activated-complex equilibrium and a crossing frequency. For a unimolecular standard-state model, k=κ(kBT/h)exp(−ΔG‡/RT). κ accounts for successful passage to the specified products; the activation free energy is not simply the overall reaction Gibbs energy.

    A reaction free-energy difference is distinct from an activation barrier.

  4. Related to
    Relationship sources · 1

    Linked statements

    • Kinetic control favours products formed more rapidly before equilibration; thermodynamic control reflects an accessible equilibrium product distribution. A lower formation barrier and a lower product free energy are different properties. Temperature, time and reversibility determine whether interconversion can occur.

    Equilibrium ratios depend on reaction Gibbs energy.

  5. Related to
    Relationship sources · 1

    Linked statements

    • Alcohol addition to a carbonyl forms a hemiacetal. Acid-catalysed replacement of its hydroxyl by another alkoxy group can produce an acetal through water loss and alcohol addition. Water activity affects the reversible equilibrium; aqueous acid can hydrolyse the acetal back to a carbonyl compound.

    Reaction composition follows the appropriate equilibrium quotient.

  6. Related to
    Relationship sources · 1

    Linked statements

    • A protein sequence and its chemical environment constrain a conformational energy landscape. Many purified proteins can refold after removal of a denaturant, while chaperones help prevent aggregation and support folding in cells. A folded state need not be a unique rigid conformation.

    Equilibrium state populations use chemical free-energy conditions.

  7. Related to
    Relationship sources · 1

    Linked statements

    • For a reversible one-to-one receptor/ligand interaction at equilibrium, the dissociation constant relates free receptor, free ligand and complex concentrations. Occupancy is hyperbolic in free ligand and reaches one-half when free ligand equals Kd. Substituting total ligand for free ligand requires a depletion assessment; washed pull-down material need not retain the original equilibrium.

    Binding affinity connects to free energy after standard states are specified.

  8. 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.

    Reaction Gibbs energy constrains the equilibrium constant.

Entry detailsPermanent link to this entry ↗
Record identity
uni-chem-gibbs-equilibrium
Revision
core.1
Structured reference record
University core expansion