1. The phenomenon of the spontaneous ow of a solvent from a solution of lower concentration to higher concentration, separated by a semipermeable membrane is called osmosis.
The excess hydrostatic pressure that builds up when the solution is separated from the solvent by a semipermeable membrane is called osmotic pressure.
2. Osmotic pressure (p) is proportional to the molar concentration/molarity (C) of the solution at a given temperature (T K).
π = CRT, where R is the gas constant.
π = \(\frac{n_B}{V}\) RT, where nB is the number of moles of the solute and V is the volume of the solution in litres.
π V = nB RT
π V = \(\frac{W_B}{M_B}\) RT, where WB is the mass of the solute and MB is the molar mass of the solute.
Or, MB = \(\frac{W_BRT}{\pi V}\)
Osmotic pressure measurement is widely used to determine molar mass of proteins, polymers and other macro molecules.