1. What is Entropy of Activation?

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.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( \Delta S^\ddagger \) — Entropy of activation (J/K·mol)
• \( R \) — Molar gas constant (8.3145 J/mol·K)
• \( A \) — Pre-exponential factor (s⁻¹)
• \( T \) — Temperature (K)
• \( N_A \) — Avogadro's number (6.022×10²³ mol⁻¹)
• \( h \) — Planck constant (6.626×10⁻³⁴ J·s)

Explanation: The formula relates the pre-exponential factor to the entropy change during activation.

3. Importance of Entropy of Activation

Details: A positive value indicates a more disordered transition state, while negative values suggest a more ordered transition state compared to reactants.

4. Using the Calculator

Tips: Enter the pre-exponential factor (from Arrhenius equation) and temperature in Kelvin. All values must be > 0.

5. Frequently Asked Questions (FAQ)

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.