Question

In the equation Rate ${\text{ = }}\,\,{\text{ZAB}}\,{\text{.}}\,{{\text{e}}^{\dfrac{{{\text{ - Ea}}}}{{{\text{RT}}}}}}$, what does ${\text{ZAB}}$ mean?

Answer 1

According to the collision theory, only a certain number of collisions between suitable reactant particles result in a perceptible or noticeable change; these successful changes are referred to as successful collisions.

Complete answer:
Max Trautz and William Lewis both suggested collision theory in the years $1916$ and $1918$, respectively.
At the moment of impact, efficient collisions must have enough energy, also known as activation energy, to sever pre-existing bonds and form all new bonds. As a consequence, the reaction's products are formed.
More collisions and hence more active collisions result from increasing the concentration of the reactant. The average kinetic energy of the molecules in a solution increases as the temperature rises, raising the number of collisions with sufficient energy.
The rate of a chemical reaction can be expressed as ${\text{ZAB}}\,{\text{.}}\,{{\text{e}}^{\dfrac{{{\text{ - Ea}}}}{{{\text{RT}}}}}}$ using collision theory.
The collision frequency of the reactants ${\text{A}}$ and ${\text{B}}$ is represented by ${\text{ZAB}}$.
When two reactant molecules collide successfully, each with the least amount of energy and the correct orientation, a reaction occurs.
In the reaction ${\text{A}}\,{\text{ + }}\,{\text{B}}\, \to \,{\text{AB}}$. The reaction rate is proportional to the number of active collisions. As a result, the reaction rate can be expressed as ${\text{ZAB}}\,{\text{.}}\,{{\text{e}}^{\dfrac{{{\text{ - Ea}}}}{{{\text{RT}}}}}}$
${\text{Ea}}\,\left( {{\text{J/mol}}} \right)$ is the activation energy.

Note:
When a catalyst is present in the collision between the reactant molecules, the chemical change requires less energy, and therefore more collisions have sufficient energy for reaction to occur. As a result, the reaction rate accelerates. Chemical kinetics and collision theory are inextricably linked.