Plug in your Pre-exponential Factor (A), Activation Energy (Eₐ), and Temperature (T) into this Arrhenius Equation Calculator to find the Rate Constant (k), along with the Exponential Term and ln(k) — or switch Calculation Mode to solve for activation energy using two rate constant–temperature pairs (k₁, T₁ and k₂, T₂).
Rate Constant (k)
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Activation Energy
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Exponential Term
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ln(k)
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The Arrhenius equation is k = A·e^(-Eₐ/RT), where k is the rate constant, A is the pre-exponential factor, Eₐ is the activation energy, R is the gas constant, and T is temperature. It describes how reaction rates depend on temperature.
Activation energy is the minimum energy required for a chemical reaction to occur. It represents the energy barrier that reactant molecules must overcome to form products. Higher activation energies result in slower reaction rates.
The pre-exponential factor A represents the frequency of collisions and the fraction of collisions with proper orientation. It's also called the frequency factor and has units that depend on the reaction order.
Temperature must be in Kelvin because the Arrhenius equation uses absolute temperature. The gas constant R is defined for Kelvin, and using Celsius or Fahrenheit would give incorrect results.
Higher temperatures increase reaction rates exponentially according to the Arrhenius equation. Even small temperature increases can dramatically increase the rate constant because of the exponential relationship.
Taking the natural logarithm gives ln(k) = ln(A) - Eₐ/(RT). This linear form allows plotting ln(k) vs 1/T to determine activation energy from the slope and the pre-exponential factor from the intercept.
Use the two-temperature form: ln(k₂/k₁) = (Eₐ/R)(1/T₁ - 1/T₂). Measure rate constants at two different temperatures, then solve for Eₐ. This method doesn't require knowing the pre-exponential factor.