Rate of a reaction can be expressed by Arrhenius equation as:
`k = Ae^(-E_(a)//RT)`
In this equation, `E_(a)` represents:

Options

A. the energy above which all the colliding molecules will react
B. the energy below which colliding molecules will not react
C. the total energy of the reacting molecules at a temperature, T
D. the fraction of molecules with energy greater than the activation energy of the reaction

Explanation

To solve the question regarding the Arrhenius equation and the meaning of \( E_a \), we will break it down step by step.

### Step 1: Understand the Arrhenius Equation
The Arrhenius equation is given by:
\[ k = Ae^{-\frac{E_a}{RT}} \]
where:
- \( k \) is the rate constant of the reaction,
- \( A \) is the pre-exponential factor,
- \( E_a \) is the activation energy,
- \( R \) is the universal gas constant, and
- \( T \) is the absolute temperature in Kelvin.

### Step 2: Identify \( E_a \)
In the context of the Arrhenius equation, \( E_a \) represents the activation energy.

### Step 3: Define Activation Energy
Activation energy (\( E_a \)) is defined as the minimum amount of energy that reactant molecules must possess to undergo a chemical reaction and form products. It is the energy barrier that must be overcome for the reaction to proceed.

### Step 4: Visualize Activation Energy
If we visualize a reaction progress diagram, we can see that:
- The reactants start at a certain energy level.
- To convert into products, the reactants must reach a peak energy level (the activation energy).
- Only when the reactants have enough energy to surpass this barrier can they successfully react to form products.

### Step 5: Conclusion
Thus, \( E_a \) is crucial because it determines the rate of the reaction. If the energy of the colliding molecules is below \( E_a \), they will not react. Therefore, the correct interpretation of \( E_a \) is that it is the energy below which the colliding molecules will not react.

### Final Answer
In conclusion, \( E_a \) represents the activation energy, which is the minimum amount of energy required for reactant molecules to undergo a chemical reaction.

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