Question

The colligative properties of a solution depend on:
(A) The number of solute particles present in it
(B) The chemical nature of the solute particles present in it
(C) The nature of the solvent used
(D) none

Answer 1

Hint: The vapour pressure of the solution decreases when a non-volatile solute is added to a volatile solvent. That means vapour pressure should vary from pure solvent to vapour pressure of the solution. There are some properties of solutions changes depending on the decrease of this vapour pressure of a solution.


Complete step by step solution:
There are many properties of solutions which are connected to the decrease in the vapour pressure of the solution. Those are:
(1) Relative lower pressure of the solvent: this property which is equal to the mole fraction of the solute and the below equation represents the relative lowering of the vapour pressure of the solvent.
\[\dfrac{{{p}^{o}}-p}{p}={{X}_{2}}\]
(2) Depression of freezing point of the solvent: according to Raoult’s law, the vapour pressure of solvent decreases when a non-volatile solvent is added, simultaneously the freezing point of the solvent decreases. Hence, depression of the freezing point of the solution is directly proportional to the molality of the solution.
\[\Delta {{T}_{f}}={{K}_{f}}m\]
(3) Elevation of the boiling point of the solvent: for a dilute solution, the molal concentration of the solute is directly proportional to the elevation of the boiling point of the solvent.
\[\Delta {{T}_{b}}={{K}_{b}}m\]
(4) Osmotic pressure of the solution: the flow of solvent particles from dilute solution to high concentration solution through the semipermeable membrane is an osmosis process and the pressure that stops the flow of solvent particles is known as osmotic pressure. The molarity (C) of the solution is proportional to the osmotic pressure of the solution.
\[\Pi =CRT\]
The above physical properties of a solution depend on the number of particles of solution or mole fraction of solute is called colligative properties.
Hence, colligative properties of a solution depend on the number of solute particles present in it


So, the correct option is A.


Note: The colligative properties which are mentioned depend on the number of solute particles irrespective of the nature related to the number of particles present in the solution. These properties are used to determine the molar mass of the solute.