Which of the following colligative property can be determined at room temperature :

Options

A. Elevation in boiling point
B. depression in freezing point
C. osmotic pressure
D. both (a) and (b)

Explanation

To determine which colligative property can be measured at room temperature, we need to analyze the properties mentioned: elevation in boiling point, depression in freezing point, and osmotic pressure.

### Step-by-Step Solution:

1. **Understanding Colligative Properties**:
- Colligative properties depend on the number of solute particles in a solution and not on the identity of the solute. The main colligative properties include:
- Elevation of boiling point
- Depression of freezing point
- Osmotic pressure

2. **Elevation in Boiling Point**:
- The elevation in boiling point (ΔT_b) is given by the formula:
\[ \Delta T_b = i \cdot K_b \cdot m \]
where \(i\) is the van 't Hoff factor, \(K_b\) is the ebullioscopic constant, and \(m\) is the molality of the solution.
- This property is typically measured at higher temperatures since it involves boiling point elevation.

3. **Depression in Freezing Point**:
- The depression in freezing point (ΔT_f) is calculated using the formula:
\[ \Delta T_f = i \cdot K_f \cdot m \]
where \(K_f\) is the cryoscopic constant.
- Similar to boiling point elevation, this property is generally measured at lower temperatures, specifically at the freezing point of the solvent.

4. **Osmotic Pressure**:
- Osmotic pressure (π) can be calculated using the formula:
\[ \pi = i \cdot C \cdot R \cdot T \]
where \(C\) is the molarity of the solution, \(R\) is the universal gas constant, and \(T\) is the temperature in Kelvin.
- Osmotic pressure can be measured at room temperature (around 24-25°C or 297-298 K) as it does not require the solution to be at its boiling or freezing point.

5. **Conclusion**:
- Among the three colligative properties, osmotic pressure is the only one that can be determined at room temperature. Elevation in boiling point and depression in freezing point are typically measured at their respective temperatures (boiling and freezing points).

### Final Answer:
**Osmotic pressure can be determined at room temperature.**

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