Question

Which of the following is an example of a colligative property?
(a) Freezing point depression
(b) Osmotic pressure
(c) Boiling point elevation
(d) Vapour pressure lowering
(e) All of the answers are correct.

Answer 1

In this question, first we have to know what are colligative properties, which materials show colligative property, what are the examples of colligative property and on which factors they depend and how.

Complete answer:
So, let’s start with definition of colligative properties:
Colligative properties: This is a property which is shown by the solutions. The property of any solution that depends only on the concentration or number of the solute particles present in the solution, not on the nature of the solution are called colligative properties.
So, now the question is which properties of a solution are colligative properties.
There are four colligative property of any solution:
(a) Freezing point depression
(b) Boiling point elevation
(c) Osmotic pressure
(d) Vapour pressure lowering
(a) Freezing point depression: It is a property of a solution which depends upon the number of solute particles, i.e, the decrease in the freezing point when there is addition of a non-volatile solute is called freezing point depression.
$\Delta {T_f} = i{K_f}m$
Where $\Delta {T_f}$ is the freezing point depression, ${K_f}$ is freezing point depression constant, $i$ is van’t hoff factor and $m$ is molarity.
(b) Boiling point elevation: It is a property of a solution which depends upon the number of solute particles, i.e, the increase in the boiling point when there is addition of a non-volatile solute is called boiling point elevation.
$\Delta {T_b} = i{K_b}m$
Where, $\Delta {T_b}$ is the boiling point depression, ${K_b}$ is boiling point depression constant, $i$ is van’t hoff factor and $m$ is molarity.
(c) Osmotic pressure: The pressure applied by the solution to prevent the flow of solute particles, when a semipermeable membrane is placed between the two liquids is called Osmotic pressure.
$\Pi = cRT$
Where, $\Pi$ is osmotic pressure, $c$ is concentration, $R$ is gas constant and $T$ is temperature.
(d) Vapour pressure lowering: When any non-volatile solute is added in a pure solvent, the vapour pressure of the solution decreases because the surface captured by the solvent decreases known as vapour pressure lowering.
${P_o} - {P_s} = {\chi _s}$
Where, ${P_o}$ is the vapour pressure of the pure solvent, ${P_s}$ is the vapour pressure of the solution and ${\chi _s}$ is the mole fraction of the solute.
Hence, all the four Freezing point depression, Osmotic pressure, Boiling point elevation and Vapour pressure lowering are the colligative properties.
Hence, the correct option is (e) All of the answers are correct.

Note: The colligative properties depend on quantity not on the quality i.e, it only depends on the concentration or number of solute particles and independent of the nature of the solution or solute. The colligative properties are physical properties.