Eyring polanyi vs arrhenius equation

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Discussion Overview

The discussion centers on the comparison between the Eyring-Polanyi equation and the Arrhenius equation, exploring their derivations, advantages, and the implications of their respective parameters. The scope includes theoretical aspects and mathematical reasoning related to chemical kinetics.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • Some participants suggest that the Eyring-Polanyi equation is more advantageous than the Arrhenius equation, though the reasons for this are not fully explored.
  • It is noted that the Arrhenius equation is considered purely empirical, while the Eyring-Polanyi equation is derived from a microscopic mechanism.
  • One participant observes that the Eyring-Polanyi equation incorporates more parameters related to the transition state, such as entropy and enthalpy, compared to the activation energy in the Arrhenius equation, questioning if this perspective is valid.
  • A later reply discusses the mathematical treatment of both equations, indicating that the Arrhenius equation yields a linear relationship when logarithmized, whereas the Eyring-Polanyi equation results in a slightly nonlinear relationship. It suggests finding an Arrhenius-like approximation to the Eyring-Polanyi equation using tangent line analysis.

Areas of Agreement / Disagreement

Participants express differing views on the advantages of the Eyring-Polanyi equation versus the Arrhenius equation, with no consensus reached on which is superior or under what conditions.

Contextual Notes

The discussion highlights the complexity of comparing the two equations, including the dependence on definitions of parameters and the implications of their mathematical forms. There are unresolved aspects regarding the interpretation of the preexponential factor in the Arrhenius equation.

aaku516
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They both are derived from same kinetic theory of gases, but I've heard that eyring polanyi equation is more advantageous over the arrhenius equation. Why do you think that is the case?
 
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Arrhenius equation is purely empirical, while the Eyring Polanyi equation is derived from the microscopic mechanism.
 
According to a brief examination of the varaibles and constants involved in the arrenhenius equation and eyring polanyi equation, what I've noticed is that there are more parameters of the transition state (such as entropy and enthalpy) involved in the eyring polanyi equation as opposed to only just the activation energy that can be determined from the arrenhrnius one, and also the preexponential factor in the arrenhenius equation doesn't really tell us much..
Am I on the right track?
 
When you logarithmize both equations, you will get a linear equation in case of the Arrhenius plot. In the case of the EP equation, the relation will be slightly nonlinear.
You can find the best Arrhenius like approximation to the EP equation from the slope and offset of the line tangent to the logarithmized EP equation at a given point.
Try to determine the values of the Arrhenius prefactor and energy this way!
 

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