unit 5 Flashcards
reaction rate
the amount of reactions that occur in a unit of time
reaction order
determines how the reaction rate depends on the concentration of the reactant
integrated rate law
relationship between the concentrations of the reactants and time
half-life
the time required for the concentration o a reactant to fall to half its initial value
activation energy (Ea)
energy barrier that has to be overcome for reactants to go to products
frequency factor (A)
number of times reactants approach the activation barrier per unit of time
activated complex/transition state
high energy state a molecule must go through to turn reactants into products- high reaction energy = low reaction rate
exponential factor
number between 0 and 1 that represents the fraction of molecules that have enough energy to make it over the energy barrier in a given approach
arrhenius plot
used in analysis of kinetic data
collision model
model that represents chemical reactions as occurring from collisions between the molecules
orientation factor
number between 0 and 1 that represents the fraction of molecules that have enough energy to make it over the energy barrier in a given approach
collision frequency
number of times reactants approach the activation barrier per unit of time (by colliding)
kinetics
rate of change of reactant or product over a unit of time during a reaction
reaction mechanism
the series of individual steps by which an overall chemical reaction occurs
elementary step
each step in a reaction mechanism
reaction intermediate
species that forms in one elementary step and is consumed in another
molecularity
number of reaction particles in the step
unimolecular
A -> products
bimolecular
A + A -> products OR A + B -> products
rate-determining step
slowest rate of the elementary steps
catalyst
substance that increases the rate of a chemical reaction but is not consumed by the reaction
homogeneous catalysis
when the catalyst exists in the same phase as the reactant(s)
heterogeneous catalysis
when the catalyst exists in a different phase than the reactant(s)
enzymes
biological catalysts that increase the rates of biochemical reactions
active site
part of the structure of an enzyme that is formed to bind to the substrate
substrate
the reactant molecule
0 order law and units
Law: Rate = k
Units: Ms to the -1 power
1st order law and units
Law: Rate= k [A]
Units: s^-1
2nd order law and units
Law: Rate= k[A]^2 or k[A][B]
Units: M^-1 times s^-1
3rd order law and units
Law: Rate= k[A]^2[B]
Units: M^-2 times s^-1
