Consider the following statements related to temperature dependence of rate constants. Identify the correct statements:…

Step 1 — Arrhenius equation: $k = A e^{-E_a/RT}$

Step 2 — Evaluate each statement

A. "Arrhenius equation holds only for elementary homogeneous reactions"

FALSE ✗ — The Arrhenius equation applies to both elementary and complex reactions, and to heterogeneous reactions as well. It is a general empirical equation.

B. "Unit of A is same as unit of k"

TRUE ✓ — Since $e^{-E_a/RT}$ is dimensionless, A must have the same units as k (s$^{-1}$ for first order, L mol$^{-1}$ s$^{-1}$ for second order, etc.)

C. "Low $E_a$ = fast reaction at given temperature"

TRUE ✓ — $k = A e^{-E_a/RT}$. Lower $E_a$ $\Rightarrow$ larger $e^{-E_a/RT}$ $\Rightarrow$ larger k $\Rightarrow$ faster reaction.

D. "A and $E_a$ depend on temperature"

FALSE ✗ — A (pre-exponential factor) and $E_a$ (activation energy) are temperature-independent constants for a given reaction. Temperature dependence of k comes through the exponential term.

E. "When $E_a >> RT$, A and $E_a$ become interdependent"

FALSE ✗ — A and $E_a$ are always independent parameters. The condition $E_a >> RT$ just means the reaction is very slow, but it does not create interdependence between A and $E_a$.

Step 3 — Answer: B and C are correct → Option (c)

Key Points to Remember:

• Arrhenius equation applies to all reactions (not just elementary)
• A and $E_a$ are temperature-independent constants
• Unit of A = unit of k (same order of reaction)
• Lower $E_a$ always means faster rate at the same temperature