Question

Which of the following statement(s) about the Arrhenius equation is/are correct?

• A. The pre-exponential factor becomes equal to the rate constant of the reaction at extremely high temperature.
• B. When the activation energy of the reaction is zero, the rate becomes independent of temperature.
• C. The term $e^{-E_a/RT}$ represents the fraction of the molecules having energy in excess of threshold value.
• D. On raising temperature, rate constant of the reaction of greater activation energy increases less rapidly than that of the reaction of smaller activation energy.

Answer 1

Answer: (A), (B), (C)

The correct options are
A The pre-exponential factor becomes equal to the rate constant of the reaction at extremely high temperature.
B When the activation energy of the reaction is zero, the rate becomes independent of temperature.
C The term $e^{-E_a/RT}$ represents the fraction of the molecules having energy in excess of threshold value.

The Arrhenius equation describes the effect of temperature on the velocity of a chemical reaction, the basis of all predictive expressions used for calculating reaction-rate constants. In the Arrhenius equation, k is the reaction rate constant, A and E are numerical constants characteristic of the reacting substances, R is the thermodynamic gas constant, and T is the absolute temperature.

Arhenius equation is $k=A{e}^{-E_a/RT}$

So when $T\to \infty ;k=A$ the rate constant becomes equal to frequency factor.

When the activation energy of the reaction is zero, $k=A$, the rate becomes independent of temperature.

Larger the activation energy of a reaction, smaller is the value of rate constant.

Larger the activation energy of a reaction, greater is the influence of change in temperature on rate constant.

For lower temperature range, increase in temperature causes more change in the value of $k$ than the same increase in temperature for high temperature range.