3.9: Key Terms
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- Aug 20, 2023
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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
