Entropy of Activation Formula:
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Definition: The entropy of activation is a thermodynamic parameter that describes the change in entropy when forming the transition state from reactants.
Purpose: It helps understand the molecularity and mechanism of chemical reactions through transition state theory.
The calculator uses the formula:
Where:
Explanation: The formula relates the pre-exponential factor to the entropy change during activation.
Details: A positive value indicates a more disordered transition state, while negative values suggest a more ordered transition state compared to reactants.
Tips: Enter the pre-exponential factor (from Arrhenius equation) and temperature in Kelvin. All values must be > 0.
Q1: What are typical values for entropy of activation?
A: For unimolecular reactions: ~0 to +50 J/K·mol; bimolecular reactions: ~-50 to -200 J/K·mol.
Q2: How does temperature affect the entropy of activation?
A: The entropy of activation is generally temperature-dependent, though often treated as constant over small temperature ranges.
Q3: What's the relationship with Gibbs free energy of activation?
A: \( \Delta G^\ddagger = \Delta H^\ddagger - T \Delta S^\ddagger \), where \( \Delta H^\ddagger \) is enthalpy of activation.
Q4: How is the pre-exponential factor determined?
A: It's typically obtained from the y-intercept of an Arrhenius plot (lnk vs 1/T).
Q5: What units should be used?
A: Ensure consistent SI units: J/K·mol for entropy, s⁻¹ for A, and K for temperature.