Consider the following statements related to temperature dependence of rate constants.
Identify the correct statements.
A. The Arrhenius equation holds true only for an elementary homogenous reaction.
B. The unit of A is same as that of k in Arrhenius equation.
C. At a given temperature, a low activation energy means a fast reaction.
D. A and Ea as used in Arrhenius equation depend on temperature.
E. When Ea ≫ RT, A and Ea become interdependent.
Choose the correct answer from the options given below:

Solution

Chemistry ma’am · 2 steps

Check each statement against what k = Ae^(-Eₐ/RT) actually says. Only B and C survive.

1. k = A e^(-Eₐ/RT)

2. Read the equation. The exponential e^(-Eₐ/RT) has no units, so A must carry the units of k. A smaller Eₐ makes the exponent less negative, so k is larger and the reaction is faster.

   Statement	True or false	Reason
   A	False	Arrhenius is an empirical law. It also fits many complex and heterogeneous reactions, not only elementary homogeneous ones.
   B	True	The exponential term is dimensionless, so A has the same unit as k.
   C	True	Lower Eₐ gives a larger e^(-Eₐ/RT), so a larger k at the same T.
   D	False	A and Eₐ are treated as constants, nearly independent of temperature over the usual range.
   E	False	When Eₐ ≫ RT, A and Eₐ are independent of temperature. Nothing ties one to the other.

3. So. Only B and C are correct, which is option (c).

The idea to keep. In k = Ae^(-Eₐ/RT), all the temperature dependence sits in the exponential. A and Eₐ are constants of the reaction, and A always shares the units of k.

Answer from the NTA final answer key. Solution by PrepWiser.