Question

In Arrhenius equation, $k=A{e}^{-E_a/RT}$. A may be termed as the rate constant at:

• A. very low temperature.
• B. very high temperature.
• C. zero activation energy.
• D. the boiling temperature of the reaction mixture.

Answer 1

Answer: (B), (C)

The correct options are
B very high temperature.
C zero activation energy.

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.