Question

Assertion: According to transition state theory for the formation of an activated complex, one of the vibrational degrees of freedom is converted into a translational degree of freedom.
Reason: Energy of the activated complex is higher than the energy of reactant molecules.
A.Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
B.Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
C.Assertion is correct but Reason is incorrect.
D.Both Assertion and Reason are incorrect.

Answer 1

Hint: This question gives the knowledge about the transition state theory. Bimolecular reaction between two molecules progresses through the formation of activated complex which then decomposes to yield the product.

Complete Answer:
Transition state is also known as activated complex theory or absolute reaction rate theory which was developed by Eyring, Polnyi and Evans in $1935$. Transition state theory explains that bimolecular reaction between two molecules progresses through the formation of activated complex which then decomposes to yield the product.
Reaction for activated complex is as follows:
$A + B \rightleftharpoons {\left( {AB} \right) } \to P$
Where $A$ and $B$ are reactants, ${\left( {AB} \right) }$ is an activated complex and $P$ is a product.
Activated complex is treated as a distinct chemical species in equilibrium with the reactants which then decomposes into the products. Activated complex is a special molecule in which one vibrational degree of freedom has been converted to a translational degree of freedom along the reaction coordinate. Activated complex is not merely an intermediate in the process involving forming or breaking of bonds. It is very unstable because it has very high potential energy differentiating between the reactants and products. When the enough amount of vibrational energy is provided to the system then only activated complex decomposes into products. The rate of reaction depends on two things, first is activated complex and second is vibrational energy.
So, this is true that one of the vibrational degrees of freedom is converted into a translational degree of freedom for the formation of an activated complex, according to transition state theory and also that the energy of the activated complex is higher than the energy of reactant molecules.

Therefore, option A is correct.

Note: Always remember that the activated complex is very unstable because it has very high potential energy differentiating between the reactants and products. It is not merely an intermediate in the process involving forming or breaking of bonds.