204. Define osmatic pressure.

Answer:

Osmotic pressure is the minimum pressurewhich needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane. It is also definedas the measure of the tendency of a solution to take in water by osmosis.

or 

osmotic pressure is proportional to the molarity, C of the solution at a given temperature T. Thus:

Π = C R T

Here Π is the osmotic pressure and R is the
gas constant.