Chemical Kinetics

Vocabulary

activated complex

intermediate configuration of atoms during a chemical reaction with high potential energy

activation energy

minimum energy needed for a chemical reaction to initiate

Arrhenius equation

equation that relates temperature to the rate constant; given as k=AeEaRTk=Ae^{-\frac{E_a}{RT}}

bimolecular reaction

elementary reaction that occurs between two reactants

catalyst

substance that causes the rate of a chemical reaction to increase

chemical kinetics

field that studies the rates of chemical reactions

collision theory

theory that describes how chemical reactions occur through molecular collisions and why reaction rates vary between reactions

elementary reaction

reaction that takes place in a single step

enzyme

biological molecule that catalyzes a biological reaction

first-order reaction

reaction in which the rate is dependent on the concentration of one of the reactants, raised to the power of one; given as a rate law with the form r=k[A]r=k\lbrack\rm{A}\rbrack

heterogeneous catalyst

catalyst that is in a different phase than that of the reactants

homogeneous catalyst

catalyst that is in the same phase as that of the reactants and is present in the reaction medium

instantaneous rate

rate of a chemical reaction at a particular moment

integrated rate law

rate law that defines concentration as a function of time

intermediate

species that is produced in one step and consumed in another step of a chemical reaction

molecularity

number of molecules that participate in the rate-determining step of a chemical reaction

rate constant (k)

constant relating reaction rate to concentrations of reactants

rate expression

mathematical expression that relates rate with a rate constant and concentrations of the reactants; given as the general form r=k[A]m[B]nr=k\lbrack{\rm{A}}\rbrack^m\lbrack{\rm{B}}\rbrack^n

rate-determining step

slowest reaction in a multistep reaction that determines the overall rate

reaction half-life

time it takes for a reactant to drop to half its starting concentration during a chemical reaction

reaction mechanism

exact step or steps required to convert reactants into products

reaction order

sum of the powers that the reactant concentrations are raised to in the rate expression

reaction rate

speed at which a reaction occurs

second-order reaction

reaction in which the sum of the powers that the reactant concentrations are raised to in the rate expression is equal to two; given as a rate law with the form r=k[A][B]r=k\lbrack{\rm A}\rbrack\lbrack{\rm B}\rbrack or r=k[A]2r=k\lbrack{\rm A}\rbrack^2

termolecular reaction

elementary reaction that occurs between three reactants

unimolecular reaction

elementary reaction with one reactant

zero-order reaction

reaction in which rate is not dependent on reactant concentrations; given as a rate law with the form r=kr=k