📉 Arrhenius Equation Calculator
Use the two-point Arrhenius equation to get the activation energy from two rate constants and temperatures, or find k at a new temperature.
Activation energy Ea
178036 J/mol
Two-point Arrhenius: ln(k₂/k₁) = −(Ea/R)·(1/T₂ − 1/T₁), R = 8.314 J/(mol·K). Temperatures in kelvin. 🔒 Computed in your browser.
How the arrhenius equation calculator works
The two-point form is ln(k₂/k₁) = −(Ea/R)·(1/T₂ − 1/T₁), with R = 8.314 J/(mol·K) and temperatures in kelvin. Enter two rate constants and their temperatures to get the activation energy Ea; or give Ea and one (k, T) pair to predict the rate constant at another temperature. A large activation energy makes ln k fall steeply as 1/T rises, so high-Ea reactions speed up sharply with heat; plotting ln k against 1/T gives a straight line of slope −Ea/R.
The standard way to extract activation energy from kinetics data without plotting. Rate constants roughly double for every 10 K near room temperature when Ea is around 50 kJ/mol.
Frequently asked questions
What is the Arrhenius equation?
k = A·e^(−Ea/RT), relating a rate constant to temperature. The two-point form, ln(k₂/k₁) = −(Ea/R)(1/T₂ − 1/T₁), lets you find the activation energy from two measurements.
How do I find activation energy from two temperatures?
Enter the two rate constants and their kelvin temperatures; the tool computes Ea = −R·ln(k₂/k₁) / (1/T₂ − 1/T₁).
What is activation energy?
The minimum energy barrier a reaction must overcome. A higher Ea means the rate is more temperature-sensitive.
Can I predict a rate constant at a new temperature?
Yes, give the activation energy and a known (k, T) pair, then solve for k₂ at the target temperature T₂.
What units is activation energy in?
This tool reports Ea in J/mol (divide by 1000 for kJ/mol), using R = 8.314 J/(mol·K).
What does the pre-exponential factor A represent?
A (the frequency factor) reflects how often reactant molecules collide with the correct orientation. In k = A·e^(−Ea/RT) it sets the ceiling rate that would apply if every collision had enough energy.
How do I read Ea from an Arrhenius plot?
Plot ln k against 1/T; the points fall on a line of slope −Ea/R. Multiply the slope by −R (8.314) to get the activation energy in J/mol.