Which factor affect the specific rate constant of a first order reaction ?

Options

A. Time for completion of reaction
B. Concentration of the reactants
C. Concentration of the products
D. Temperature of reaction

Answer

To determine which factors affect the specific rate constant (k) of a first-order reaction, we can analyze the equation for the rate constant and the factors involved:

### Step-by-Step Solution:

1. **Understanding the Rate Constant (k)**:
The specific rate constant (k) for a first-order reaction is given by the equation:
\[ k = Ae^{-\frac{E_a}{RT}} \]
where:
- \( A \) is the frequency factor (pre-exponential factor),
- \( E_a \) is the activation energy,
- \( R \) is the universal gas constant,
- \( T \) is the temperature in Kelvin.

2. **Identifying the Factors**:
From the equation, we can identify the factors that affect the rate constant \( k \):
- **Temperature (T)**: The rate constant is directly affected by the temperature. As the temperature increases, the value of \( k \) increases due to the exponential term \( e^{-\frac{E_a}{RT}} \).
- **Activation Energy (E_a)**: Changes in the activation energy will also affect \( k \). A lower activation energy results in a higher rate constant, while a higher activation energy results in a lower rate constant.
- **Frequency Factor (A)**: While the frequency factor is generally considered a constant for a given reaction, it can be influenced by the nature of the reactants and the reaction conditions.

3. **Conclusion**:
The specific rate constant \( k \) for a first-order reaction is primarily affected by:
- Temperature (T)
- Activation Energy (E_a)
- Frequency Factor (A)