Question

Can a reaction have zero Activation Energy?

Answer 1

We have to know that the Arrhenius equation is an expression for the temperature dependence of rates of reaction. The equation was formulated by Svante Arrhenius in the year 1889. A significant application of Arrhenius equation is in obtaining the rate of chemical reactions and for determining the energy of activation.

Complete answer: We have to know that the Arrhenius equation is useful in determining the rate of reaction and plays an essential portion in chemical kinetics. We can write Arrhenius equation as,
$K = A{e^{ - {E_a}/RT}}$
Here, K represents the rate constant
A represents the pre-exponential factor
${E_a}$ represents the energy of activation
R represents the gas constant
T represents the temperature (in Kelvin)
The activation energy ${E_a}$of a reaction is the limit which should be overcome for the reactants to be transformed to form products. A fast reaction happens, if the energy of activation is low. A slow reaction happens, if the activation energy is high.
We can say activation energy as the minimum possible quantity of energy (minimum) that is necessary to initiate a reaction or the quantity of energy existing in a chemical system for a reaction to occur.
Let us take ${E_a} = 0$, then based on Arrhenius equation,
$K = A{e^{ - {E_a}/RT}}$
$K = A{e^0}$
$K = A$
This indicates that every collision could lead to a chemical reaction that cannot be true. Thus, a chemical reaction could not have zero energy of activation.

Note: We have to remember that the fundamentals of Arrhenius equation is collision theory. According to this theory, a reaction takes place due to collision between two molecules to form an intermediate. An unstable intermediate is formed and is present for a shorter period of time. With the support of the Arrhenius equation, we could determine the temperature, presence of catalyst, frequency, orientation of collisions, and effect of energy barrier.