Activation Energy Calculator
Use the Arrhenius equation to compute the activation energy of a reaction from two rate constants measured at different temperatures.
Activation energy
74.85 kJ/mol
Pre-exponential factor A
19,766,428,827.76 1/s
How to Use This Calculator
Measure rate constants
Obtain reaction rate constants at two distinct temperatures (k₁ at T₁ and k₂ at T₂).
Enter temperature in Kelvin
Convert °C to Kelvin by adding 273.15 before entering values.
Review activation energy
The calculator applies the Arrhenius equation to determine activation energy in kJ/mol.
Use the pre-exponential factor
A can be used to predict rate constants at other temperatures via the full Arrhenius expression.
Formula
ln(k₂ / k₁) = (−Eₐ / R) × (1/T₂ − 1/T₁)
Rearranging gives Eₐ = R ln(k₂/k₁) / ((1/T₁) − (1/T₂)). R is the gas constant (8.314 J·mol⁻¹·K⁻¹).
Example
For k₁ = 1.0e-3 s⁻¹ at 298 K and k₂ = 3.0e-3 s⁻¹ at 308 K, Eₐ ≈ 57 kJ/mol.
Full Description
Activation energy reflects the minimum energy required for a reaction to proceed. The Arrhenius equation relates rate constants to temperature, enabling activation energy estimation from experimental data.
This calculator streamlines the analysis by accepting two rate constants at different temperatures and outputting both activation energy and the pre-exponential factor for further kinetic modeling.
Frequently Asked Questions
Can I use Celsius directly?
No. Convert to Kelvin by adding 273.15 to maintain correct units in the Arrhenius equation.
Do rate constants need the same units?
Yes. Ensure k₁ and k₂ share identical units so they cancel in the ratio.
What if k₂ < k₁?
The equation still works. The sign of ln(k₂/k₁) accounts for rate decreases at lower temperatures.
Can I compute k at a new temperature?
Yes. Use k = A e^(−Eₐ/RT). The calculator supplies A and Eₐ for this purpose.
Is the Arrhenius equation exact?
It is an approximation. Deviations occur for complex mechanisms or when activation energy varies with temperature.