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The Arrhenius Equation (solving for k) calculator computes the chemical reaction rate (k) based on a collision rate (A), activation energy (Ea) and a temperature (T).
INSTRUCTIONS: Choose your units and enter the following:
- (A) Frequency factor (total number of collisions per second)
- (Ea) Activation energy, typically in Joules per mole (J/mol).
- (T) Temperature
Chemical Reaction Rate: The calculator computes the rate (k) in units of per second (s-1 aka perSec). However this can be automatically converted in many other frequency units via the pull-down menu.
Related Calculators:
The Math
The fraction of molecules whose energy equals or exceeds the activation energy is proportional to e-Ea/RT, thus resulting in the Arrhenius equation. Therefore, the rate constant, k, must be proportional to the same factor. The Arrhenius Equation calculates the temperature dependence of the chemical reaction rate constant and can also be used to show the effect of a change of temperature on the rate constant and on the rate of the chemical reaction.
k=A⋅e−EaRT
- A = frequency factor (total number of collisions per second)
- E_a = activation energy (J/mol, cal/mol)
- T = temperature (K)
- R = gas law constant = 8.314 J/(mol_K)
The variable "A" is referred to as the Arrhenius constant or "pre-exponential" constant. It is the maximum rate constant that would be observed if every collision resulted in a reaction. It is the product of the collision frequency factor (Z) and the steric factor (ρ) as in:
A=Zρ
The steric factor accounts for the orientation of the molecules needed to result in a reaction between two molecules.
Uses
The Arrhenius Equation is used to show how a change in temperature effects the rate constant of a reaction. For example, if the rate constant doubles, then so does the rate of the reaction.
Description
It is noted that every reaction has an energy barrier or minimum energy to start the reaction. When a reaction increases with increasing temperature, it implies that only molecules with sufficient energy are able to react. The energy barrier or minimum energy a molecule must have to overcome this barrier is called activation energy (Ea).
Molecules must possess an energy that is equal or higher than the activation energy, Ea to undergo reaction. At low temperature, only a few molecules have sufficient energy - the reaction will proceed, but at a slow rate. At higher temperate, more molecules are able to surpass the energy barrier and the reaction proceeds at a faster rate.
A is measured in seconds−1
Activation Energy (Ea) is in kJmol
Temperature (T) is in Kelvin
Supplemental Material
Khan Academy: Arrhenius Equation
References
See also:
Arrhenius Equation Algebraic Method (vCalc)
The variable "A" is referred to as the Arrhenius constant or pre-exponential constant. It is the maximum rate constant that would be observed if every collision resulted in a reaction. It is the product of the collision frequency factor (Z) and the steric factor (ρ) as in:
The steric factor accounts for the orientation of the molecules needed to result in a reaction between two molecules.
The variable "A" is referred to as the Arrhenius constant or pre-exponential constant. It is the maximum rate constant that would be observed if every collision resulted in a reaction. It is the product of the collision frequency factor (Z) and the steric factor (ρ) as in:
The steric factor accounts for the orientation of the molecules needed to result in a reaction between two molecules.
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