Calculate rate constants, activation energy, or pre-exponential factor from temperature data.
Single Temperature mode: Enter any two of k, A, and Ea (plus temperature) to solve for the third. This is useful when you know the Arrhenius parameters and want to predict the rate constant at a specific temperature.
Two Temperature mode: Enter rate constants measured at two different temperatures to determine the activation energy. This is the standard experimental approach — measure k at two (or more) temperatures and extract Ea from the slope.
The Arrhenius equation k = A × e^(−Ea/RT) describes how reaction rate constants depend on temperature. A is the pre-exponential (frequency) factor, Ea is the activation energy, R = 8.314 J/(mol·K), and T is absolute temperature in Kelvin.
The two-temperature form rearranges to: ln(k₂/k₁) = (Ea/R) × (1/T₁ − 1/T₂), allowing Ea to be determined from just two rate constant measurements.
Worked example: A reaction has k = 0.015 s⁻¹ at 300 K and k = 0.12 s⁻¹ at 350 K. Ea = R × ln(k₂/k₁) / (1/T₁ − 1/T₂) = 8.314 × ln(0.12/0.015) / (1/300 − 1/350) = 8.314 × 2.079 / (4.76×10⁻⁴) = 36,300 J/mol = 36.3 kJ/mol.
Rule of thumb: For many reactions near room temperature, a 10°C increase roughly doubles the rate. This corresponds to an activation energy of about 50–60 kJ/mol.