How this calculator works
Use rate coefficients with the same reaction order and units. The one-temperature method needs an independently known frequency factor; the two-temperature method eliminates it while assuming it stays constant. Temperature is converted to kelvins. Negative apparent activation energies are allowed because complex mechanisms can show them. The result characterizes the chosen temperature range, not necessarily a single elementary barrier.
Formula
k = A exp(-Ea/RT); Ea = RT ln(A/k); Ea = R ln(k2/k1)/(1/T1 - 1/T2). R = 8.31446261815324 J/(mol K).
Worked example
At 300 K, A/k = e gives Ea = 2494.338785 J/mol. If A = k, Ea = 0 at any positive temperature.
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Frequently asked questions
Must activation energy be positive?
An elementary barrier is normally positive, but an apparent value for a multistep process can be negative.
Can I use Celsius?
Yes. The unit selector converts Celsius to absolute kelvins before calculation.
What happens at equal temperatures?
Two identical temperatures provide no temperature dependence, so the two-point calculation is undefined.