Question

Unit of Frequency factor (A) is:
A.$mol/L$
B.$mol/L \times s$
C.depends upon order
D.unitless

Answer 1

We must know that the frequency factor is the pre-exponential constant of Arrhenius equation. The Arrhenius equation is the relation between the temperature and the rate coefficient.

Complete step by step answer:
Let’s start with discussing the frequency factor (A), frequency factor or more commonly known as pre-exponential factor in Arrhenius equation is a pre-exponential constant in Arrhenius equation. The Arrhenius equation is the relation between the temperature and the rate coefficient. The Arrhenius equation is given by:
$k = A{e^{ - Ea/RT}}$
Where, A is frequency factor.
It is to be noted that the units of the frequency factor is strictly dependent on the order of the reaction. For the First order reaction the unit of frequency factor is ${s^{ - 1}}$.
So the answer to this question is option C i.e depends upon order.

Additional Information: Arrhenius equation is used to determine the changes in rate of reaction due the temperature as it is the relation between the temperature and the rate constant k.
Frequency factor for different orders are, for first order reaction it is ${s^{ - 1}}$, for second order it is $Lmo{l^{ - 1}}{s^{ - 1}}$.

Note:
The rate of reaction has application; it is normal to understand that any industry which works in the field of chemistry would love to know whether they can fasten the reaction or slow down the reaction. One of the ways to do this is by changing the temperature but how much temperature change will be sufficient is determined using Arrhenius Equation.