Term | Definition |
chemical kinetics | area of chemistry that concerns reaction rates |
reaction rate | change in concentration of a reactant or product per unit of time |
instantaneous rate | value of the rate at a particular time |
rate law | also known as differential rate law |
rate constant | property constant in the relationship between reaction rates and reactant concentration |
order | positive or negative exponent determined by experiment of reactant concentration in a rate law |
differential rate law | experiment gives rate of reaction as a function of concentration often called the rate law |
integrated rate law | exponent that shows the concentration of a reactant as a function of time |
method of initial rates | method for experimentally determining the form of the rate law for a reaction |
initial rate | instantaneous rate determined just after reaction begins |
overall reaction order | sum of n + m |
first order reaction | rate of reaction depends on a concentration to the first power |
integrated first order rate law | will always plot a straight line |
half life of a reactant | time required for a reactant to reach 1/2 its original concentration |
integrated second order rate law | rate of reaction depends on concentration to second power |
zero order reaction | rate is always constant |
integrated zero order rate law | plot of concentration of A versus t gives a straight line slope of -k |
pseudo first order rate law | law obtained by simplification of a more complicated one |
reaction mechanism | series of elementary steps involved in chemical reaction |
intermediate | species is neither a reactant nor a product but is formed and consumed in the reaction sequence |
elementary step | reaction whose rate law can be written from its molecularity |
molecularity | number of species that must collide to produce the reaction represented by an elemental step in a reaction mechanism |
unimolecular step | reaction step involving only 1 molecule |
bimolecular step | reaction involving collision of 2 molecules |
termolecular step | reaction involving the simultaneous collision of 3 molecules |
rate-determining step | slowest step in a reaction mechanism, determines overall rate |
collision model | model based on an idea that molecule must collide to react used to account for observed characteristics of reaction rates |
activation energy | threshold energy that must be overcome to produce a chemical reaction |
activated complex (transition state) | arrangement of atoms found at top of potential energy barrier as a reaction proceeds from reactants to products |
molecular orientation | orientation of molecules during collision some of which can lead to reaction while others cannot |
steric factor | factor (always less than 1) reflects fraction of collisions with orientation that can produce a chemical reaction |
Arrhenius equation | equation representing rate constant as k=Ae ^-E/RT |
frequency factor | A replaces zp |
enzyme | large molecule, usually a protein that catalyzes biological reactions |
catalyst | substance that speeds up a reaction without being consumed |
homogeneous catalyst | present in the same phase as reacting molecules |
heterogeneous catalyst | exists in different phases |
adsorption | collection of 1 substance on the surface of another |