Which of the following colligative properties is associated with the concentration term molarity ?

Options

A. Lowering of vap.pressure
B. Osmotic pressure
C. Depression in f.p.
D. Elevation in b.p.

Answer

To solve the question, "Which of the following colligative properties is associated with the concentration term molarity?", we can follow these steps:

### Step 1: Understand Colligative Properties
Colligative properties are properties of solutions that depend on the number of solute particles in a given amount of solvent, rather than the identity of the solute. Common colligative properties include vapor pressure lowering, boiling point elevation, freezing point depression, and osmotic pressure.

**Hint:** Remember that colligative properties depend on the number of solute particles, not their nature.

### Step 2: Identify the Concentration Terms
We need to identify which colligative properties use molarity as the concentration term. Molarity (M) is defined as the number of moles of solute per liter of solution.

**Hint:** Recall the definition of molarity and how it is calculated.

### Step 3: Analyze Each Colligative Property
1. **Vapor Pressure Lowering**: The formula for vapor pressure lowering is given by:
\[ \Delta P = P^0 - P = P^0 \cdot X_{solute} \]
where \(X_{solute}\) is the mole fraction of the solute. This does not use molarity.

2. **Boiling Point Elevation**: The formula is:
\[ \Delta T_b = K_b \cdot m \]
where \(m\) is the molality of the solution, not molarity.

3. **Freezing Point Depression**: The formula is:
\[ \Delta T_f = K_f \cdot m \]
Again, \(m\) refers to molality.

4. **Osmotic Pressure**: The formula is:
\[ \Pi = CRT \]
where \(C\) is the molarity of the solution. This is the only colligative property that directly uses molarity.

**Hint:** Compare the formulas for each colligative property to see which one includes molarity.

### Step 4: Conclusion
From the analysis, we conclude that the colligative property associated with the concentration term molarity is **osmotic pressure**.

**Final Answer:** The colligative property associated with molarity is **osmotic pressure**.