Activation Energy Calculator
Find the activation energy (Ea) of a chemical reaction using the Arrhenius equation. Enter rate constants measured at two temperatures to calculate Ea, Q₁₀, and see how temperature affects reaction rate. Essential for reaction kinetics and chemical engineering.
Rate constant at temperature 1
Rate constant at temperature 2
Temperature in Kelvin for k₁
Temperature in Kelvin for k₂
Frequency factor for Arrhenius equation
Temperature in Kelvin
What is activation energy?
Activation energy (Ea) is the minimum energy required to initiate a chemical reaction. Even exothermic reactions need an energy "push" to start. It represents the energy barrier between reactants and the transition state. Higher activation energy means slower reactions; catalysts lower the activation energy to speed up reactions.
How is activation energy calculated?
Activation energy is calculated using the Arrhenius equation: ln(k₂/k₁) = -Ea/R × (1/T₂ - 1/T₁). You need rate constants at two different temperatures. Measure reaction rate at two temperatures, calculate k values, plug into the equation to solve for Ea. Our calculator handles this automatically.
What units does activation energy use?
Activation energy is typically expressed in kilojoules per mole (kJ/mol) orkilocalories per mole (kcal/mol). Common conversions: 1 kcal = 4.184 kJ. Typical values: 50-250 kJ/mol for most reactions, under 50 for very fast reactions, over 150 for very slow reactions.
What is the Arrhenius equation?
The Arrhenius equation relates rate constant to temperature: k = A × e^(-Ea/RT), where k is rate constant, A is pre-exponential factor, Ea is activation energy, R is gas constant (8.314 J/mol·K), and T is temperature in Kelvin. It predicts how reaction rate changes with temperature.
What is Q₁₀?
Q₁₀ is the temperature coefficient: how much the rate increases for each 10°C increase. Most reactions have Q₁₀ between 2-3, meaning rate doubles (Q₁₀ = 2) or triples (Q₁₀ = 3) with a 10°C rise. Our calculator shows your specific Q₁₀ based on your data. Reactions with Q₁₀ > 3 are very temperature-sensitive.
How does temperature affect reaction rate?
Higher temperatures increase reaction rates exponentially (via Arrhenius). A 10°C rise typically doubles or triples the rate. This is why reactions in refrigerators slow dramatically, and why heating accelerates cooking, decomposition, and chemical synthesis. The activation energy determines temperature sensitivity.
What is a catalyst?
Catalysts speed reactions by lowering activation energy—they provide an alternative pathway with lower Ea. They don't change thermodynamics or yield, just rate. Enzymes are biological catalysts with very low Ea for specific reactions. Catalysts aren't consumed; they can be reused unless inhibited or deactivated.