Arrhenius parameter (A) depends on

Options

A. Steric factor
B. Collision frequency
C. Both (1) & (2)
D. Neither (1) nor (2)

Answer

To determine what the Arrhenius parameter (A), also known as the pre-exponential factor, depends on, we can analyze the Arrhenius equation and the factors that influence the rate of a chemical reaction.

### Step-by-Step Solution:

1. **Understanding the Arrhenius Equation**:
The Arrhenius equation is given by:
\[ k = A e^{-\frac{E_a}{RT}} \]
where:
- \( k \) = rate constant
- \( A \) = pre-exponential factor (Arrhenius parameter)
- \( E_a \) = activation energy
- \( R \) = universal gas constant
- \( T \) = temperature (in Kelvin)

2. **Identifying the Role of A**:
The pre-exponential factor \( A \) represents the frequency of collisions and the orientation of the reacting molecules. It indicates how many molecules collide with the proper orientation to react.

3. **Factors Affecting A**:
- **Collision Frequency**: This is the number of collisions that occur per unit time. Higher collision frequency increases the likelihood of reactions occurring.
- **Steric Factor**: This factor accounts for the orientation of the colliding molecules. For a reaction to occur, molecules must collide in a specific orientation. If the orientation is not favorable, the reaction may not proceed even if the molecules collide.

4. **Conclusion**:
Therefore, the Arrhenius parameter \( A \) depends on:
- The frequency of collisions (collision frequency).
- The steric factor (which considers the orientation of the molecules during collisions).

Thus, we conclude that the Arrhenius parameter \( A \) depends on both the collision frequency and the steric factor.

### Final Answer:
The Arrhenius parameter \( A \) depends on:
- Collision frequency
- Steric factor