Step 1 (Identification of Colligative Properties): [0.5 Mark]

Colligative properties depend on the number of solute particles in a solution. Based on NCERT Chemistry (Solutions Chapter), the standard formulas are:

• Osmotic pressure ($\pi$): Defined by the van't Hoff equation: $$\pi = CRT$$
• Elevation of boiling point ($\Delta T_{\text{b}}$): Defined as: $$\Delta T_{\text{b}} = K_{\text{b}}m$$
• Depression of freezing point ($\Delta T_{\text{f}}$): Defined as: $$\Delta T_{\text{f}} = K_{\text{f}}m$$
• Relative lowering of vapour pressure: Defined by Raoult's Law: $$\frac{P_1^0 - P_1}{P_1^0} = \frac{W_2 \times M_1}{M_2 \times W_1}$$

Step 2 (Mapping Column I to Column II): [0.25 Mark]

By comparing the definitions above with the provided columns:

• a (Osmotic pressure) matches with ii ($\pi = CRT$)
• b (Elevation of boiling point) matches with iv ($\Delta T_{\text{b}} = K_{\text{b}}m$)
• c (Depression of freezing point) matches with i ($\Delta T_{\text{f}} = K_{\text{f}}m$)
• d (Relative lowering of vapour pressure) matches with iii ($\frac{P_1^0 - P_1}{P_1^0} = \frac{W_2 \times M_1}{M_2 \times W_1}$)

Step 3 (Final Concluded Answer): [0.25 Mark]

The correct sequence is a-ii, b-iv, c-i, d-iii. Therefore, the correct option is (D).

💡 EL10 Concept Insight: Think of colligative properties like counting how many "party guests" (solute particles) are in a room; it doesn't matter who they are, just how many there are, which changes how the "room" (the solvent) behaves—like how much pressure it needs to stop flowing or how much heat it needs to boil!