The increase in equivalent conductivity of a weak electrolyte with dilution is due to :

Options

A. increase in degree of dissociation and decrease in ionic mobility
B. decrease in degree of dissociation and decrease in ionic mobility
C. increase in degree of dissociation and increase in ionic mobility
D. decrease in degree of dissociation and increase in ionic mobility

Answer

To solve the question regarding the increase in equivalent conductivity of a weak electrolyte with dilution, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Weak Electrolytes**:
- A weak electrolyte is a substance that does not completely dissociate into ions in solution. For example, when a weak electrolyte like acetic acid (CH₃COOH) is dissolved in water, it partially dissociates into CH₃COO⁻ and H⁺ ions.

**Hint**: Remember that weak electrolytes do not fully dissociate, which is key to understanding their behavior in solution.

2. **Effect of Dilution**:
- When a weak electrolyte is diluted, the volume of the solution increases. This increase in volume leads to a decrease in molarity (concentration) of the electrolyte, as molarity is defined as the number of moles of solute per unit volume of solution.

**Hint**: Consider how dilution affects concentration; as volume increases, concentration decreases.

3. **Understanding Equivalent Conductivity**:
- Equivalent conductivity (Λ) is defined as the conductivity (κ) of the solution multiplied by a factor that accounts for the dilution (1000 divided by normality). Normality is related to molarity and the number of ions produced by the electrolyte.

**Hint**: Remember the formula for equivalent conductivity: Λ = κ × (1000 / N), where N is normality.

4. **Relationship Between Molarity and Equivalent Conductivity**:
- As dilution occurs, the molarity decreases, which leads to an increase in equivalent conductivity. This is because the ions can move more freely in a more dilute solution, enhancing their ability to conduct electricity.

**Hint**: Focus on how dilution affects the movement of ions and thus the conductivity of the solution.

5. **Degree of Dissociation and Ionic Mobility**:
- With increased dilution, the degree of dissociation of the weak electrolyte increases. This means more ions are present in the solution. Additionally, the ionic mobility of these ions also increases because they have more space to move around without encountering other ions.

**Hint**: Consider how more ions and increased space for movement contribute to conductivity.

6. **Conclusion**:
- Therefore, the increase in equivalent conductivity of a weak electrolyte with dilution is due to both an increase in the degree of dissociation and an increase in ionic mobility.

**Final Answer**: The correct statement is: "Increase in degree of dissociation and increase in ionic mobility."