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Showing 91–120 of 1709 reference entries

ChemistryReaction rates and empirical rate laws

Reaction rate measures change over time; a rate law describes its dependence under specified conditions.

MethodChemistryCatalysis and equilibrium

A catalyst changes the reaction pathway and rate, while preserving the equilibrium constant for the same reaction.

ModelBiologyCells as units of life

Cell theory describes the organization and reproduction of cellular life.

ModelBiologyDNA and sequence information

DNA's base sequence stores biological information.

DefinitionBiologyGene expression

Gene expression produces functional RNA or protein from gene information.

DefinitionBiologyDNA replication

Complementary base pairing allows DNA strands to serve as copying templates.

ModelBiologyCell cycle, mitosis and cytokinesis

DNA duplication, nuclear division and cytoplasmic division are distinct events in a typical mitotic cycle.

ModelBiologyMeiosis and chromosome segregation

Typical diploid meiosis halves the number of chromosome sets through two divisions after one DNA replication.

ModelBiologyAlleles and Mendelian segregation

A diploid individual's paired alleles can segregate into gametes.

ModelBiologyBiological evolution

Evolution concerns inherited change across generations.

DefinitionBiologyNatural selection

Heritable variation can change through differences in reproductive contribution.

ModelBiologyGenetic drift

Chance can change allele frequencies independently of an adaptive advantage.

ModelBiologyCommon ancestry and branching lineages

Evolutionary relationships describe descent from shared ancestors.

ModelBiology · ChemistryMetabolism and chemical pathways

Metabolism comprises the regulated chemical reactions of living systems.

DefinitionBiologyOxygenic photosynthesis

Oxygenic photosynthesis couples light-energy capture to carbon fixation and releases oxygen from water.

ModelBiologyAerobic cellular respiration

Aerobic respiration couples nutrient oxidation to ATP production, using oxygen as the final electron acceptor.

ModelBiologyMembranes and transport

Selective membranes and transport proteins regulate movement between a cell and its surroundings.

ModelBiologyEcology and ecosystems

Ecology examines organisms' interactions with one another and their physical environment.

DefinitionBiologyHomeostasis and negative feedback

Feedback can maintain internal variables within functional ranges.

ModelEarth & cosmosRock cycle and geological transformation

Rock materials can change through multiple geological pathways.

ModelEarth & cosmosPlate tectonics

Moving lithospheric plates organize many large-scale geological processes.

ModelEarth & cosmosEarth's water cycle

Water moves among reservoirs above, on and below Earth's surface.

ModelEarth & cosmos · Biology · ChemistryEarth's carbon cycle

Carbon moves through biological, oceanic, atmospheric and geological reservoirs.

ModelEarth & cosmosPlanetary radiative energy balance

Earth's energy storage changes when incoming and outgoing energy differ.

ModelEarth & cosmosAtmospheric greenhouse effect

Infrared absorption and emission affect how Earth loses heat to space.

ModelEarth & cosmosWeather, climate and their time scales

Weather describes short-term conditions; climate describes their longer-term patterns.

DefinitionEarth & cosmosOrbits as gravitational motion

An orbiting body can remain in continuous gravitational free fall.

ModelEarth & cosmosStellar fusion and evolution

Main-sequence stars release energy by fusing hydrogen into helium.

ModelEarth & cosmosHot Big Bang and the cosmic microwave background

Expansion and relic radiation support an earlier hot, dense Universe.

ModelMathematics & logicFirst-order predicates and quantifiers

Quantifiers bind variables over a specified domain.

Definition
ModelSource checked

Catalysis and equilibrium

Chemistry

A catalyst changes the reaction pathway and rate, while preserving the equilibrium constant for the same reaction.

Key knowledge

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.

Conditions and scope

  • Compare the same reaction at the same temperature; changed conditions, binding or side reactions require separate accounting.
  • Regeneration is a reaction-cycle statement, not a promise of unlimited catalyst lifetime or a change in thermodynamic favourability.
Sources · 4

References

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

  1. Paul Flowers, Klaus Theopold, Richard Langley and William R. Robinson — OpenStax, Rice University2 sources
    1. Chemistry 2e, 12.7: CatalysisPaul Flowers, Klaus Theopold, Richard Langley and William R. Robinson — OpenStax, Rice UniversityTextbook chapteropenstax.orgRead source
    2. Chemistry 2e, 13.3: Shifting Equilibria — Effect of a CatalystPaul Flowers, Klaus Theopold, Richard Langley and William R. Robinson — OpenStax, Rice UniversityTextbook chapteropenstax.orgRead source
  2. Physical Sciences 12: CatalystsSiyavulaTextbook chaptersiyavula.comRead source
  3. Chemistry XII: Chemical KineticsNCERTTextbook chapter · PDFncert.nic.inRead source

Evidence and review

Published alternative-pathway diagrams and forward/reverse acceleration account; no catalyst performance test was conducted.

2026-10-10 · English kinetic/thermodynamic distinction checked against sections 12.7 and 13.3, especially Effect of a Catalyst.

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

Alternative pathways and an unchanged equilibrium constant for the same reaction.

A faster approach to equilibrium does not change its thermodynamic position.

Related reference entries

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

Showing 1–5 of 5 relationships

Scientific relationships · 5 / 5

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

  1. Related to
    Relationship sources · 1

    Linked statements

    • Reaction rates describe how quickly reactants are consumed or products formed. A rate law relates a measured rate to composition under specified conditions. For an overall reaction, its reaction orders must be established from kinetic evidence rather than simply copied from the balanced equation's coefficients.
    • 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.

    Catalysis changes a reaction pathway and thereby its rate under the specified conditions.

  2. Related to
    Relationship sources · 1

    Linked statements

    • 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.

  3. Related to
    Relationship sources · 1

    Linked statements

    • In a common mononuclear two-electron oxidative addition, a substrate bond is replaced by two metal–ligand bonds and the metal's formal oxidation state increases by two. Reductive elimination reverses that accounting by forming a ligand–ligand bond. These transformations connect steps in catalytic cycles, with several possible detailed mechanisms.

    The transformations can form steps in catalyst regeneration.

  4. Related to
    Relationship sources · 1

    Linked statements

    • The twelve green-chemistry design principles address waste prevention, incorporation of reactant atoms, reduced synthesis hazards, lower product toxicity, suitable auxiliaries, energy demand, renewable material sources, avoiding temporary chemical modifications, catalytic transformations, post-use breakdown, process monitoring and accident potential. These are design aims whose performance needs evidence; a renewable input or catalyst does not alone establish an environmentally preferable process.

    Catalytic transformations are one design strategy; outcomes remain process-dependent.

  5. Uses definition
    Relationship sources · 1

    Linked statements

    • Enzymes are biological catalysts, most of which are proteins. A substrate is a reactant engaged by the enzyme; an active site provides the local binding and catalytic environment. Chemical groups, geometry and molecular motion influence substrate recognition and reaction pathways. Induced fit describes conformational changes associated with binding, rather than a perfectly rigid lock-and-key structure. Temperature, pH and regulatory interactions can alter catalytic activity without making one enzyme's optimum universal.

    Enzyme action is biological catalysis and preserves the specified equilibrium free-energy difference.

Entry detailsPermanent link to this entry ↗
Record identity
chem-catalysis
Revision
core.1
Structured reference record
Essential core · first collection