The pre-exponential factor in Arrhenius equation is also known as :
A. Arrhenius constant.
B. Frequency factor.
C. Activation energy.
D. pre-exponential factor.
Choose the correct answer from the options given below.
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → A, B and D only
The Arrhenius equation relates the rate constant to temperature:
\( \displaystyle k=A\,e^{-E_a/RT} \)
A stands in front of the exponential term, so it is called the pre-exponential factor; the book also calls it the Arrhenius factor and the frequency factor, the last because it is related to how often the molecules collide. Ea is a different quantity: the activation energy in the exponent.
(A) Arrhenius constant. — Correct. A is the constant of the Arrhenius equation for a given reaction.
(B) Frequency factor. — Correct. A is related to the frequency of collisions between reacting molecules.
(C) Activation energy. — Incorrect. Ea is the energy barrier in the exponent. A has the same unit as k, whereas Ea is measured in J mol−1.
(D) pre-exponential factor. — Correct. This is the name of A itself, since it appears before the exponential term.
NCERT (2026-27 edition):
Temperature Dependence of the Rate of a Reaction – …
