Statement I: Except osmotic pressure, all the other colligative prope…

The correct answer is Option (4) → Statement I is incorrect but Statement II is correct.

Colligative properties depend on how many solute particles are present, not on what they are. The four are relative lowering of vapour pressure, elevation of boiling point, depression of freezing point and osmotic pressure.

Statement I: Except osmotic pressure, all the other colligative properties depend on the nature of the solvent. — False. The relative lowering of vapour pressure is equal to the mole fraction of the solute:

    \( \displaystyle \frac{p_1^{\circ}-p_1}{p_1^{\circ}}=x_2 \)

It has the same value for the same mole fraction of solute whatever the solvent, so it is a second colligative property that does not depend on the nature of the solvent. Only the elevation of boiling point and the depression of freezing point change with the solvent, through its K_b and K_f.

Statement II: Colligative properties depend on the number of solute particles irrespective of their nature relative to the total number of particles present in the solution. — True. This is the definition of a colligative property.

NCERT (2026-27 edition):
1.6 Colligative Properties and Determination of Molar Mass – “… All these properties depend on the number of solute particles irrespective of their nature relative to the total number of particles present in the solution.”

Summary – “… The vapour pressure of the solvent is lowered by the presence of a non-volatile solute in the solution and this lowering of vapour pressure of the solvent is governed by Raoult’s law, according to which the relative lowering of vapour pressure of the solvent over a solution is equal to the mole fraction of a non-volatile solute present in the solution.”