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Enthalpy-Entropy Compensation (EEC) Effect: Decisive Role of Free Energy
Animesh Pan1, Tanmoy Kar1, Animesh K Rakshit1
1Centre for Surface Science, Department of Chemistry and ‡Indian Society for Surface Science & Technology, Department of Chemistry, Jadavpur University , Kolkata 700032, India.
The Journal of Physical Chemistry. B
|September 9, 2016
Summary
Enthalpy-entropy compensation (EEC) is a puzzling thermodynamic phenomenon. This study reveals that considering Gibbs free energy (ΔG) alongside enthalpy (ΔH) and entropy (ΔS) demonstrates that conventional EEC plots are mathematically unsound.
Area of Science:
- Chemical Thermodynamics
- Physical Chemistry
Background:
- The
- enthalpy-entropy compensation
- (EEC) effect is a poorly understood phenomenon in chemical thermodynamics.
- Various explanations exist, including empirical, extrathermodynamic, error-related, and solvation effects.
- Recent theories propose statistical reasons and hidden Carnot's cycles.
Purpose of the Study:
- To re-evaluate the conventional understanding of EEC.
- To investigate the role of Gibbs free energy (ΔG) in enthalpy-entropy correlations.
- To establish a mathematically sound framework for analyzing EEC.
Main Methods:
- Analysis of enthalpy (ΔH) and entropy (ΔS) data for similar processes.
- Incorporation of Gibbs free energy (ΔG) into thermodynamic analyses.
- Examination of authentic literature data to assess EEC correlations.
Main Results:
- Conventional EEC plots, focusing only on ΔH and ΔS, are mathematically inappropriate.
- Consideration of ΔG reveals that correlations can be linear, nonlinear, or absent.
- The study addresses phenomena of non-compensation and anti-compensation.
Conclusions:
- A realistic understanding of EEC requires the simultaneous consideration of ΔG, ΔH, and ΔS.
- Further studies with a wide range of ΔG values are needed for accurate evaluation of EEC and related phenomena.
- The findings challenge the conventional interpretation of enthalpy-entropy compensation.
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