Osmotic pressure is measured by

Options

A. Ostwald's method
B. Berkeley and Hartley method
C. Preffer's method
D. Beckmann's method

Answer

To measure osmotic pressure, we can follow a systematic approach using the Berkley and Hartley method. Here’s a step-by-step solution:

### Step-by-Step Solution:

1. **Understanding Osmotic Pressure**:
- Osmotic pressure is the pressure required to stop the flow of solvent through a semi-permeable membrane when there is a concentration gradient.

2. **Setting Up the Apparatus**:
- Use an apparatus that consists of a semi-permeable membrane separating two compartments. One side contains pure solvent (water), and the other side contains a solution with a lower concentration of solvent.

3. **Initial Conditions**:
- On one side of the membrane, place the pure solvent, which has an osmotic pressure denoted as π1. On the other side, place the solution with a higher concentration of solute.

4. **Observation of Osmosis**:
- Allow the system to reach equilibrium. The solvent will naturally move from the side with pure solvent (higher concentration of solvent) to the side with the solution (lower concentration of solvent) until equilibrium is reached.

5. **Applying External Pressure**:
- To measure the osmotic pressure, apply external pressure to the side containing the solution. This pressure must be just enough to stop the movement of the solvent across the membrane.

6. **Determining Osmotic Pressure**:
- The external pressure applied to halt the flow of solvent is equal to the osmotic pressure (π1) of the solution. Therefore, we can conclude that:
\[ \text{Osmotic Pressure} (\pi) = \text{External Pressure} (P_{\text{external}}) \]

7. **Conclusion**:
- The method used to measure osmotic pressure is known as the Berkley and Hartley method, which is the simplest and most effective way to determine osmotic pressure in a solution.