Energy Changes and Rates of Reaction
Chemical kinetics describe the rates and mechanisms by which chemicals react. As a result, it has enormous potential for describing chemical processes as well as natural phenomena. The simplest representation of chemical kinetics is the collision theory, which describes a chemical reaction as the collision between two atoms or molecules resulting in a chemical reaction ("successful collisions"). As a result, the reaction rate (rA) is proportional to the concentration of the reactants. For example the rate law of the reaction A + B --> AB could be written as:
rA = k[A][B]
Where [A] and [B] are concentrations of the two reactants, and k is a constant which describes the number of successful collisions per unit time.
rA = k[A][B]
Where [A] and [B] are concentrations of the two reactants, and k is a constant which describes the number of successful collisions per unit time.
The Arrhenius Equation - Calculating the proportionality constant (k)
It stands to reason that the number of successful collisions per unit time is a fraction of the total number of collisions per unit time. That is to say, if atoms or molecules collide, they either react or do not react. The Arrhenius Equation was proposed by Svante Arrhenius in 1889 as a simple, yet accurate representation of the number of successful reactions as a function of temperature:
k = A*exp(-EA/(RT))
Where EA is the activation energy (J), R is the universal gas constant (J mol-1 K-1), T is the temperature (K) and A is the total number of collisions per unit time.
It stands to reason that the number of successful collisions per unit time is a fraction of the total number of collisions per unit time. That is to say, if atoms or molecules collide, they either react or do not react. The Arrhenius Equation was proposed by Svante Arrhenius in 1889 as a simple, yet accurate representation of the number of successful reactions as a function of temperature:
k = A*exp(-EA/(RT))
Where EA is the activation energy (J), R is the universal gas constant (J mol-1 K-1), T is the temperature (K) and A is the total number of collisions per unit time.