Question

Explain osmotic pressure of solution. Establish a relationship between osmotic pressure of solution and molar mass of solute.

Hint:

Osmotic pressure measurements are a practical way to determine the molar mass of large biomolecules like proteins and polymers.

Answer 1

Step 1: Definition of Osmotic Pressure.
Osmotic pressure is the pressure required to stop the flow of solvent molecules through a semipermeable membrane from pure solvent to solution. It is a colligative property and depends on the number of solute particles in solution, not their nature.
Step 2: Mathematical Expression.
The osmotic pressure is given by: \[ \pi = CRT \] where, - \(\pi\) = osmotic pressure
- \(C\) = molar concentration of solute
- \(R\) = gas constant
- \(T\) = absolute temperature Step 3: Relation with Molar Mass.
Molar concentration can be written as: \[ C = \frac{n}{V} = \frac{w}{M \cdot V} \] where, - \(w\) = mass of solute
- \(M\) = molar mass of solute
- \(V\) = volume of solution (in litres) Substituting in the osmotic pressure formula: \[ \pi = \frac{wRT}{MV} \] Conclusion:
The relation between osmotic pressure and molar mass of solute is: \[ M = \frac{wRT}{\pi V} \]