Eyring polanyi vs arrhenius equation

[aaku516]

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?

 

[DrDu]

Arrhenius equation is purely empirical, while the Eyring Polanyi equation is derived from the microscopic mechanism.

 

[aaku516]

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?

 

[DrDu]

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!

 

[LudusRex]

The Eyring-Polanyi and Arrhenius equations are both important concepts in the field of chemical kinetics, which studies the rates of chemical reactions. While they are both derived from the same kinetic theory of gases, there are some key differences between them.

The Arrhenius equation, proposed by Swedish chemist Svante Arrhenius in 1889, relates the rate of a chemical reaction to the temperature and the activation energy of the reaction. It assumes that all molecules in a reaction have the same kinetic energy and only differ in their orientation and energy barriers. This equation has been widely used to explain the temperature dependence of reaction rates and has been successful in predicting many reactions.

On the other hand, the Eyring-Polanyi equation, proposed by American physical chemist Henry Eyring and Hungarian chemist Michael Polanyi in the 1930s, takes into account the concept of transition state theory. It considers the energy and entropy changes that occur during the transition from reactants to products and incorporates the concept of activation enthalpy and activation entropy. This equation has been found to be more accurate in predicting reaction rates, especially for complex reactions involving multiple steps and intermediates.

One of the main advantages of the Eyring-Polanyi equation over the Arrhenius equation is its ability to account for the effects of pressure and solvent on reaction rates. The Arrhenius equation only considers the effect of temperature, while the Eyring-Polanyi equation takes into account the changes in the transition state energy and entropy due to changes in pressure and solvent.

Additionally, the Eyring-Polanyi equation has been found to be more accurate at high temperatures and for reactions involving large molecules. This is because the Arrhenius equation assumes that all molecules have the same kinetic energy, which may not be the case for larger molecules with more complex structures.

In conclusion, while both the Eyring-Polanyi and Arrhenius equations are important tools in the study of reaction rates, the Eyring-Polanyi equation offers more advantages due to its incorporation of transition state theory and its ability to account for the effects of pressure and solvent. It has been found to be more accurate and applicable to a wider range of reactions, making it a valuable tool in the field of chemical kinetics.