In respect of the equation k = Ae^{-E_a/RT} in chemical kinetics, which one of the following stateme

Q: Why is $A$ called the pre-exponential factor?

Because it literally appears before the exponential term in the Arrhenius equation! It represents the frequency of collisions with the correct orientation.

Q: Is $R$ the Rydberg constant here?

No, in the context of thermodynamics and kinetics, $R$ is always the Universal Gas Constant ($8.314 \text{ J K}^{-1} \text{ mol}^{-1}$).

Q: Can $k$ be the equilibrium constant?

No, $k$ (lowercase) is the rate constant. The equilibrium constant is usually denoted by a capital $K$.

Q: What does the exponential term $e^{-E_a/RT}$ represent?

It represents the fraction of molecules that have kinetic energy equal to or greater than the activation energy $E_a$.

Q: Why is $A$ not the adsorption factor?

Adsorption is a surface phenomenon. The Arrhenius equation applies to reaction rates in general, where $A$ is related to collision frequency, not adsorption.

Question

In respect of the equation $k = Ae^{-E_a/RT}$ in chemical kinetics, which one of the following statements is correct ?

Options:

(A) $k$ is equilibrium constant

(B) $A$ is adsorption factor

(C) $E_a$ is energy of activation

(D) $R$ is Rydberg constant

Sigma Percentile · Accepted Answer

### The Heart of Chemical Kinetics

Imagine you are trying to push a heavy boulder over a hill. The height of the hill represents the energy barrier you must overcome.

In chemical kinetics, this energy barrier is known as the **Activation Energy**, denoted by $E_a$.

The Arrhenius equation beautifully captures this physical reality, linking the rate of a reaction to temperature and this energy barrier.

$$k = A e^{-\frac{E_a}{RT}}$$

Let's break down this elegant equation piece by piece to understand what each term truly represents.

### Decoding the Terms

First, we have $k$, which is the **rate constant** of the reaction. It tells us how fast the reaction proceeds at a given temperature.

Next is $A$, known as the **pre-exponential factor** or frequency factor. It represents the total number of collisions between reactant molecules that have the correct orientation to react.

Then comes the exponential term, $e^{-\frac{E_a}{RT}}$. This is the **Boltzmann factor**.

It represents the fraction of those perfectly oriented collisions that actually possess enough kinetic energy to overcome the activation energy barrier.

Inside this exponent, $R$ is the **Universal Gas Constant** ($8.314 	ext{ J K}^{-1} 	ext{ mol}^{-1}$), and $T$ is the **absolute temperature** in Kelvin.

### Analyzing the Options

Now, let's look at the options provided in the question.

Option (a) suggests $k$ is the equilibrium constant. This is incorrect; $k$ is the rate constant, while the equilibrium constant is typically denoted by a capital $K$.

Option (b) claims $A$ is the adsorption factor. As we discussed, $A$ is the pre-exponential factor related to collision frequency, not adsorption.

Option (d) states $R$ is the Rydberg constant. In thermodynamics and kinetics, $R$ is always the Universal Gas Constant.

This leaves us with Option (c), which correctly identifies $E_a$ as the **energy of activation**.

Therefore, the correct statement is that $E_a$ is the energy of activation.

Animated Solution for Chemistry - Chemical Kinetics: In respect of the equation $k = A e^{- E_{a} / R T}$ in chemical kinetics, which one of the following statements is correct ?

Select Answer:

Visualized Solution

The Arrhenius Equation

Rate Constant and Pre-exponential Factor

Activation Energy and Thermodynamics

Conclusion

The Sigma Insight: Theories of Chemical Reaction

The Heart of Chemical Kinetics

Decoding the Terms

Analyzing the Options

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Animated Solution for Chemistry - Chemical Kinetics: .math-text-wrapper .katex { font-size: 1.05em !important; } .math-text-wrapper .katex-display { margin: 1rem 0 !important; } In respect of the equation k=Ae−Ea​/RT in chemical kinetics, which one of the following statements is correct ?