Chapter 6, Problem 6.7DQ

Interpretation Introduction

Interpretation:

The formulation of eyering equation has to be described along with the reason of its superiority from collision theory of reaction rates.

Concept Introduction:

Collision theory of reaction rate:

The collision theory states that when suitable particles of the reactant hit each other, only a certain fraction of collisions cause any noticeable or significant chemical change, these successful changes are called successful collisions.  The successful collisions must have enough energy known as activation energy at the moment of impact to break the pre-existing bonds and form all new bonds.  This results in the products of the reaction.  Increasing in the concentration of the reactants or increasing the temperature rate of the reaction increases as the collision rate increases.  When a catalyst is involved in the collision between the reactant molecules, less energy is required for the reaction to take place and hence more collisions have sufficient energy for reaction to occur.  Thus the reaction rate increases.  Collision theory is related to chemical kinetics.

For a reaction between A and B the collision frequency can be expressed as,

  $\text{z}\text{=}\sqrt{\text{2}}{\text{πσ}}^{\text{2}}{\text{cN}}_{\text{A}}$

Where,

$\text{z}$ is the collision frequency

$\text{σ}$ is the area of collision

$\text{c}$ is the average velocity of molecules

${\text{N}}_{\text{A}}$ is the Avogadro’s number.

Transition state theory:

In transition state theory it is supposed that an activated complex is in equilibrium with the reactants and the rate at which the complex forms products, depends on the rate at which it passes through a transition state.

Eyering equation:

The eyering equation is based on the transition state theory and it is used to describe the temperature dependence of reaction rate.  It is more likely to Arrhenius equation.