Question

Osmosis and osmotic pressure are two important terms related to solutions.

1. Explain these terms. 

2. How will he determine the molar mass of a substance by this method?

Answer 1

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 n_B is the number of moles of the solute and V is the volume of the solution in litres.

π V = n_B RT

π V = \(\frac{W_B}{M_B}\) RT, where W_B is the mass of the solute and M_B is the molar mass of the solute.

Or,  M_{B =} \(\frac{W_BRT}{\pi V}\)

Osmotic pressure measurement is widely used to determine molar mass of proteins, polymers and other macro molecules.