Read the passage carefully and answer the questions.

The osmotic pressure is one of the four colligative properties which depends on the number of particles of solute in the solution, irrespective of their nature. The osmotic pressure is equal to the product of concentration, gas constant and temperature. It is the most commonly used property for the determination of the molar mass of biomolecules. In many situations, the molecules get dissociated or associated when they are dissolved in a solvent, thereby changing the number of molecules in the solution. As a result, an abnormal molecular mass is obtained. The extent of dissociation or association is given by van't Hoff factor (i), which is the ratio of normal molar mass to abnormal molar mass. It is related with the degree of association or ionization. The introduction of van't Hoff factor in the osmotic pressure equation modifies the equation.

Which one of the following has minimum osmotic pressure at 298 K?

1 M glucose solution.

The correct answer is Option (2) → 1 M glucose solution.

Osmotic pressure is given by the formula:

$\Pi = i C R T$

Where:

• i = van’t Hoff factor (number of particles in solution)
• C = molarity

Step 1: Calculate i × C for each solution

1. 3 M KCl → KCl → 2 ions → $iC = 2 × 3 = 6$
2. 1 M glucose → non-electrolyte → 1 ion → $iC = 1 × 1 = 1$
3. 2 M urea → non-electrolyte → 1 ion → $iC = 1 × 2 = 2$
4. 2 M K₂SO₄ → 3 ions → $iC = 3 × 2 = 6$

Step 2: Compare osmotic pressures

• Lower iC → lower osmotic pressure

$1\ \text{M glucose (iC = 1)} < 2\ \text{M urea (iC = 2)} < 3\ \text{M KCl (iC = 6)} = 2\ \text{M K₂SO₄ (iC = 6)}$

✅ Answer: 1 M glucose solution