Question

Define Osmotic pressure. How will you show that Osmotic pressure is a colligative property?

Hint:

Colligative properties (vapour pressure lowering, boiling point elevation, freezing point depression, and osmotic pressure) depend only on the number of solute particles, not their type.

Answer 1

Step 1: Definition.
Osmotic pressure is the excess pressure applied to a solution to prevent the inward flow of solvent molecules across a semipermeable membrane. Step 2: Expression for osmotic pressure.
\[ \pi = CRT \] where, \(\pi\) = osmotic pressure, \(C\) = molar concentration of solute, \(R\) = gas constant, \(T\) = absolute temperature. Step 3: Proof as a colligative property.
From the equation, osmotic pressure depends only on the number of solute particles (\(C\)) in a given volume of solution, and not on their nature. Therefore, it is a colligative property. Conclusion:
Osmotic pressure is directly proportional to solute concentration and depends only on the number of solute particles, hence it is a colligative property.