Reaction rate constant

In <a href="/facts/Chemical_kinetics/D8vyX4aE">chemical kinetics</a>, a reaction rate constant or reaction rate coefficient (⁠
 
 
 
 k
 
 
 {\displaystyle k}
 
⁠) is a proportionality constant which quantifies the rate and direction of a <a href="/facts/Chemical_reaction/GpqWlKrz">chemical reaction</a> by relating it with the concentration of reactants.
For a reaction between reactants A and B to form a product C,

a A + b B → c C
where

A and B are reactants
C is a product
a, b, and c are <a href="/facts/Stoichiometric_coefficient/I5p9cJzV">stoichiometric coefficients</a>,
the <a href="/facts/Reaction_rate/Prwvxq0y">reaction rate</a> is often found to have the form:

 
 
 
 r
 =
 k
 [
 
 A
 
 
 ]
 
 m
 
 
 [
 
 B
 
 
 ]
 
 n
 
 
 
 
 {\displaystyle r=k[\mathrm {A} ]^{m}[\mathrm {B} ]^{n}}

Here ⁠
 
 
 
 k
 
 
 {\displaystyle k}
 
⁠ is the reaction rate constant that depends on temperature, and [A] and [B] are the <a href="/facts/Molar_concentration/P2WL5b9q">molar concentrations</a> of substances A and B in <a href="/facts/Mole_(unit)/kCMFwCc0">moles</a> per unit volume of solution, <a href="/facts/Presupposition/IsdPl2Ub">assuming</a> the reaction is taking place throughout the volume of the solution. (For a reaction taking place at a boundary, one would use moles of A or B per unit area instead.)
The exponents m and n are called partial <a href="/facts/Orders_of_reaction/VK18zUhN">orders of reaction</a> and are not generally equal to the stoichiometric coefficients a and b. Instead they depend on the <a href="/facts/Reaction_mechanism/9lanyVuy">reaction mechanism</a> and can be determined experimentally. 
Sum of m and n, that is, (m + n) is called the overall order of reaction.

Reaction rate constant open-in-new

Reaction rate constant