12.9: Key Terms
- Page ID
- 452529
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| Words (or words that have the same definition) | The definition is case sensitive | (Optional) Image to display with the definition [Not displayed in Glossary, only in pop-up on pages] | (Optional) Caption for Image | (Optional) External or Internal Link | (Optional) Source for Definition |
|---|---|---|---|---|---|
| (Eg. "Genetic, Hereditary, DNA ...") | (Eg. "Relating to genes or heredity") |  | The infamous double helix | https://bio.libretexts.org/ | CC-BY-SA; Delmar Larsen |
| Word(s) | Definition | Image | Caption | Link | Source |
|---|---|---|---|---|---|
| activated complex | (also, transition state) unstable combination of reactant species formed during a chemical reaction | ||||
| activation energy (Ea) | minimum energy necessary in order for a reaction to take place | ||||
| Arrhenius equation | mathematical relationship between a reaction’s rate constant, activation energy, and temperature | ||||
| average rate | rate of a chemical reaction computed as the ratio of a measured change in amount or concentration of substance to the time interval over which the change occurred | ||||
| bimolecular reaction | elementary reaction involving two reactant species | ||||
| catalyst | substance that increases the rate of a reaction without itself being consumed by the reaction | ||||
| collision theory | model that emphasizes the energy and orientation of molecular collisions to explain and predict reaction kinetics | ||||
| elementary reaction | reaction that takes place in a single step, precisely as depicted in its chemical equation | ||||
| frequency factor (A) | proportionality constant in the Arrhenius equation, related to the relative number of collisions having an orientation capable of leading to product formation | ||||
| half-life of a reaction (tl/2) | time required for half of a given amount of reactant to be consumed | ||||
| heterogeneous catalyst | catalyst present in a different phase from the reactants, furnishing a surface at which a reaction can occur | ||||
| homogeneous catalyst | catalyst present in the same phase as the reactants | ||||
| initial rate | instantaneous rate of a chemical reaction at t = 0 s (immediately after the reaction has begun) | ||||
| instantaneous rate | rate of a chemical reaction at any instant in time, determined by the slope of the line tangential to a graph of concentration as a function of time | ||||
| integrated rate law | equation that relates the concentration of a reactant to elapsed time of reaction | ||||
| intermediate | species produced in one step of a reaction mechanism and consumed in a subsequent step | ||||
| method of initial rates | common experimental approach to determining rate laws that involves measuring reaction rates at varying initial reactant concentrations | ||||
| molecularity | number of reactant species involved in an elementary reaction | ||||
| overall reaction order | sum of the reaction orders for each substance represented in the rate law | ||||
| rate constant (k) | proportionality constant in a rate law | ||||
| rate expression | mathematical representation defining reaction rate as change in amount, concentration, or pressure of reactant or product species per unit time | ||||
| rate law | (also, rate equation) (also, differential rate laws) mathematical equation showing the dependence of reaction rate on the rate constant and the concentration of one or more reactants | ||||
| rate of reaction | measure of the speed at which a chemical reaction takes place | ||||
| rate-determining step | (also, rate-limiting step) slowest elementary reaction in a reaction mechanism; determines the rate of the overall reaction | ||||
| reaction diagram | used in chemical kinetics to illustrate various properties of a reaction | ||||
| reaction mechanism | stepwise sequence of elementary reactions by which a chemical change takes place | ||||
| reaction order | value of an exponent in a rate law (for example, zero order for 0, first order for 1, second order for 2, and so on) | ||||
| termolecular reaction | elementary reaction involving three reactant species | ||||
| unimolecular reaction | elementary reaction involving a single reactant species |