The molal elevation/depression constant depends upon -

Options

A. Nature of solvent
B. Nature of solute
C. Temperature
D. `DeltaH` solution

Answer

To answer the question about what the molal elevation (Kb) and depression (Kf) constants depend on, we can break down the solution into several steps:

### Step-by-Step Solution:

1. **Understanding Kb and Kf**:
- Kb is the molal elevation constant, which is used to calculate the increase in boiling point when a solute is added to a solvent.
- Kf is the molal depression constant, which is used to calculate the decrease in freezing point when a solute is added to a solvent.

**Hint**: Remember that Kb is for boiling point elevation and Kf is for freezing point depression.

2. **Formulas for Elevation and Depression**:
- The formula for boiling point elevation is given by:
\[ \Delta T_b = K_b \times m \]
- The formula for freezing point depression is given by:
\[ \Delta T_f = K_f \times m \]
- Here, \( \Delta T_b \) and \( \Delta T_f \) are the changes in boiling and freezing points, respectively, and \( m \) is the molality of the solution.

**Hint**: Identify the variables in the equations to understand how they relate to Kb and Kf.

3. **Dependency on Solvent**:
- The values of Kb and Kf are specific to the solvent being used. They do not change with the type of solute added to the solvent.
- For example, the Kb and Kf for water (H2O) will remain constant regardless of the solute.

**Hint**: Focus on the fact that Kb and Kf are properties of the solvent.

4. **Nature of Solute**:
- The nature of the solute does not affect the values of Kb and Kf. These constants are intrinsic properties of the solvent.
- Therefore, adding different solutes will not change the Kb or Kf values for a given solvent.

**Hint**: Remember that while the solute affects the overall properties of the solution, it does not affect the constants Kb and Kf.

5. **Temperature Independence**:
- Kb and Kf are also independent of temperature. They remain constant for a given solvent at different temperatures.

**Hint**: Consider how physical properties can be affected by temperature, but note that Kb and Kf are exceptions.

6. **Conclusion**:
- The molal elevation and depression constants (Kb and Kf) depend solely on the nature of the solvent. Therefore, the correct answer to the question is that these constants depend on the solvent.

**Hint**: Summarize your findings by stating that Kb and Kf are solvent-dependent properties.

### Final Answer:
The molal elevation constant (Kb) and the molal depression constant (Kf) depend on the nature of the solvent.