# 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 $k=Ae^{-\frac{E_a}{RT}}$

### 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 $r=k\lbrack\rm{A}\rbrack$

### 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 $r=k\lbrack{\rm{A}}\rbrack^m\lbrack{\rm{B}}\rbrack^n$

### 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 $r=k\lbrack{\rm A}\rbrack\lbrack{\rm B}\rbrack$ or $r=k\lbrack{\rm A}\rbrack^2$

### 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 $r=k$