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In chemical kinetics
Chemical kinetics

Chemical kinetics, also known as reaction kinetics, is the study of reaction rate of chemical processes. Chemical kinetics includes investigations of how different experimental conditions can influence the speed of a chemical reaction and yield information about the reaction mechanism and transition states, as well as the construction of ma...
 a reaction rate constant k or quantifies the speed of a chemical reaction
Chemical reaction

A chemical reaction is a process that always results in the interconversion of chemical substances. The substance or substances initially involved in a chemical reaction are called reactants....
 .

For a chemical reaction
Chemical reaction

A chemical reaction is a process that always results in the interconversion of chemical substances. The substance or substances initially involved in a chemical reaction are called reactants....
 where substance A and B are reacting to produce C, the reaction rate
Reaction rate

The reaction rate or rate of reaction for a reactant or product in a particular chemical reaction is intuitively defined as how fast a reaction takes place....
 has the form:

k(T) is the reaction rate constant that depends on temperature.

[X] is the concentration
Concentration

In chemistry, concentration is the measure of how much of a given chemical substance there is mixed with another substance. This can apply to any sort of chemical mixture, but most frequently the concept is limited to homogeneous solutions, where it refers to the amount of solute in the solvent....
 of substance X in moles per volume of solution assuming the reaction is taking place throughout the volume of the solution. (for a reaction taking place at a boundary it would denote something like moles of X per area.)

The exponents m and n are called orders and depend on the reaction mechanism
Reaction mechanism

In chemistry, a reaction mechanism is the step by step sequence of elementary reactions by which overall chemical change occurs .Although only the net chemical change is directly observation for most chemical reactions, experiments can often be designed that suggest the possible sequence of steps in a reaction mechanism....
.






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In chemical kinetics
Chemical kinetics

Chemical kinetics, also known as reaction kinetics, is the study of reaction rate of chemical processes. Chemical kinetics includes investigations of how different experimental conditions can influence the speed of a chemical reaction and yield information about the reaction mechanism and transition states, as well as the construction of ma...
 a reaction rate constant k or quantifies the speed of a chemical reaction
Chemical reaction

A chemical reaction is a process that always results in the interconversion of chemical substances. The substance or substances initially involved in a chemical reaction are called reactants....
 .

For a chemical reaction
Chemical reaction

A chemical reaction is a process that always results in the interconversion of chemical substances. The substance or substances initially involved in a chemical reaction are called reactants....
 where substance A and B are reacting to produce C, the reaction rate
Reaction rate

The reaction rate or rate of reaction for a reactant or product in a particular chemical reaction is intuitively defined as how fast a reaction takes place....
 has the form:

k(T) is the reaction rate constant that depends on temperature.

[X] is the concentration
Concentration

In chemistry, concentration is the measure of how much of a given chemical substance there is mixed with another substance. This can apply to any sort of chemical mixture, but most frequently the concept is limited to homogeneous solutions, where it refers to the amount of solute in the solvent....
 of substance X in moles per volume of solution assuming the reaction is taking place throughout the volume of the solution. (for a reaction taking place at a boundary it would denote something like moles of X per area.)

The exponents m and n are called orders and depend on the reaction mechanism
Reaction mechanism

In chemistry, a reaction mechanism is the step by step sequence of elementary reactions by which overall chemical change occurs .Although only the net chemical change is directly observation for most chemical reactions, experiments can often be designed that suggest the possible sequence of steps in a reaction mechanism....
. They can be determined experimentally.

A single-step reaction can also be written as

Ea is the activation energy
Activation energy

In chemistry, activation energy is a term introduced in 1889 by the Swedish scientist Svante Arrhenius, that is defined as the energy that must be overcome in order for a chemical reaction to occur....
 and R is the Gas constant
Gas constant

The gas constant is a physical constant which is featured in a large number of fundamental equations in the physical sciences, such as the ideal gas law and the Nernst equation....
. Since at temperature
Temperature

In physics, temperature is a physical property of a Physical system that underlies the common notions of hot and cold; something that feels hotter generally has the greater temperature....
 T the molecules have energies according to a Boltzmann distribution
Boltzmann distribution

In physics and mathematics, the Boltzmann distribution is a certain distribution function or probability measure for the distribution of the states of a system....
, one can expect the proportion of collisions with energy greater than Ea to vary with e-Ea/RT. A is the pre-exponential factor
Pre-exponential factor

In chemical kinetics, the preexponential factor or A factor is the pre-exponential constant in the Arrhenius equation, an empirical relationship between temperature and rate coefficient....
 or frequency factor.

The Arrhenius equation
Arrhenius equation

The Arrhenius equation is a simple, but remarkably accurate, formula for the temperature dependence of the rate constant, and therefore, rate of a chemical reaction....
 gives the quantitative basis of the relationship between the activation energy
Activation energy

In chemistry, activation energy is a term introduced in 1889 by the Swedish scientist Svante Arrhenius, that is defined as the energy that must be overcome in order for a chemical reaction to occur....
 and the reaction rate
Reaction rate

The reaction rate or rate of reaction for a reactant or product in a particular chemical reaction is intuitively defined as how fast a reaction takes place....
 at which a reaction proceeds.

The units of the rate coefficient depend on the global order of reaction
Order of reaction

The Order of reaction , in chemical kinetics, with respect to a certain reactant, is defined as the Exponentiation to which its concentration term in the rate equation is raised ....
:
  • For order zero, the rate coefficient has units of mol
    Mole (unit)

    The mole is a Units of measurement of amount of substance: it is an SI base unit, and one of the few units used to measure this physical quantity....
     L
    Litre

    The litre or liter is a unit of volume. There are two official symbols: the Latin letter L in lower and upper case . The lower case L is often written as a cursive l to avoid confusion with the number 1 in antiqua fonts....
    -1 s
    Second

    The second , sometimes abbreviated sec., is the name of a units of measurement of time, and is the International System of Units SI base unit of time....
    -1 or mol dm-3 s-1
  • For order one, the rate coefficient has units of s-1
  • For order two, the rate coefficient has units of L mol-1 s-1 or mol-1 dm3 s-1
  • For order n, the rate coefficient has units of mol1-n Ln-1 s-1 or mol1-n dm3n-3 s-1


See also

Reaction rate
Reaction rate

The reaction rate or rate of reaction for a reactant or product in a particular chemical reaction is intuitively defined as how fast a reaction takes place....