Chapter 19: Chemical Kinetics
intermediate
A species that is produced in one step of a reaction mechanism and subsequently consumed in another step is called an
catalyst
A species that is first consumed and later regenerated is called a
Transition state
Activated complex is also called a
heterogenous or homogenous
Catalysis may be
Activation energy
Ea =
reactant concentration, temperature, surface area, and catalysis
Factors that influence reaction rate are
different phases
If a catalysis is heterogenous, the catalyst and reactants exist in
same phase
If a catalysis is homogenous, the catalysis and reactants exist in the
rate-determing step
If one step in a reaction is much slower than all the other steps, it is the
product formation
Only effective collisions can result in
instantaneous rate
Rates may be expressed as an average rate over a given time interval or as an
collide
Reactions occur when molecules of sufficient energy
molecularity
The rate law of each step in a reaction mechanism indicates the
Arrhenius equation
The relationship between temperature and the rate constant is expressed by the
Enzymes
are biological catalysts with high specificity for the reactions they catalyze.
Effective collisions
are those that result in the formation of an activated complex
integrated rate law
can be used to determine reactant concentrations after a specified period of time. It can also be used to determine how long it will take to reach a specified reactant concentration
zeroth-order reaction
does not depend on reactant concentration.
Collision Theory
explains why the rate constant, and therefore the reaction rate, increases with increasing temperature.
rate law
is an equation that expresses the relationship between rate and reactant concentrations.
unimolecular step
is first order, involving just one molecule
first order reaction
is proportional to the concentration of a single reactant.
second-order reaction
is proportional to the product of two reactant concentrations or the concentration of a single reactant squared.
bimolecular step
is second order, involving the collision of two molecules;
Activation energy
is the minimum energy that colliding molecules must possess in order for the collision to be effective.
reaction order
is the power to which the concentration of a given reactant is raised in the rate law equation.
half life
is the time it takes for half of a reactant to be consumed.
A reaction mechanism
may consist of a series of steps called elementary reactions.
Catalysis
refers to the process by which a catalyst increases the reaction rate.
Reaction rate
refers to the speed at which a chemical reaction occurs.
The rate constant
relates the rate of reaction with the concentrations of reactions
elementary reactions.
series of steps for a reaction mechanism are called
catalyst
speeds up a reaction, usually by lowering the value of the activation energy
initial rate
the instantaneous rate of reaction when the reactant concentrations are starting concentrations.
termolecular step
third order, involving the collision of three molecules