Question

Which of the following statements are correct:

• A. When $T\to \infty$ the rate constant becomes equal to frequency factor.
• B. Rate constant (k) always increases with the increase in temperature.
• C. Larger the value of activation energy, higher is the value of rate constant.
• D. Rate constant (k) is inversely proportional to the frequency factor (A).

Answer 1

Answer: (A), (B)

When $T\to \infty$ the rate constant becomes equal to frequency factor.
Rate constant (k) always increases with the increase in temperature.

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.

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.