What is osmotic pressure ? Why it is a colligative property ?

Explanation

### Step-by-Step Solution:

**Step 1: Definition of Osmotic Pressure**
Osmotic pressure is defined as the minimum excess pressure that must be applied to a solution to prevent the flow of solvent into it through a semi-permeable membrane. This pressure is necessary to stop the natural process of osmosis, where solvent molecules move from an area of lower solute concentration (the pure solvent) to an area of higher solute concentration (the solution).

**Step 2: Explanation of Osmosis**
In osmosis, the solvent moves through a semi-permeable membrane from a region of higher solvent concentration (pure solvent) to a region of lower solvent concentration (solution) until equilibrium is reached. The semi-permeable membrane allows the passage of solvent molecules but not solute particles.

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