Which one is the best colligative property for determination of molecular mass of polymer?

Options

A. osmotic pressure
B. elevation in boiling point
C. depression in freezing point
D. osmosis

Answer

To determine the best colligative property for the determination of the molecular mass of a polymer, we will analyze the options provided and evaluate their effectiveness.

### Step-by-Step Solution:

1. **Understanding Colligative Properties**:
Colligative properties depend on the number of solute particles in a solution rather than their identity. The main colligative properties are:
- Osmotic Pressure
- Elevation in Boiling Point
- Depression in Freezing Point

2. **Evaluating Each Option**:
- **Option A: Osmotic Pressure**:
Osmotic pressure is the pressure required to stop the flow of solvent into a solution through a semipermeable membrane. It is directly proportional to the concentration of the solute and can be measured accurately, especially in dilute solutions.

- **Option B: Elevation in Boiling Point**:
This property depends on the number of solute particles and can be used to determine molecular mass, but it is less sensitive than osmotic pressure, especially for polymers.

- **Option C: Depression in Freezing Point**:
Similar to boiling point elevation, freezing point depression can also be used to determine molecular mass, but it is affected by the solid-liquid equilibrium and may not be as precise for large molecules like polymers.

- **Option D: Osmosis**:
Osmosis is the process of solvent moving through a semipermeable membrane from a dilute solution to a concentrated one. While related to osmotic pressure, it is not a direct measurement property.

3. **Conclusion**:
After evaluating the options, osmotic pressure (Option A) is the best colligative property for determining the molecular mass of a polymer. This is because it provides a high and easily measurable value in dilute solutions, making it more accurate for large molecular weights typical of polymers.

### Final Answer:
**The best colligative property for the determination of molecular mass of a polymer is Option A: Osmotic Pressure.**