Determination of molar mass from osmotic pressure

Determination of molar mass from osmotic pressure

According to van’t Hoff equation

 Ï€=cRT

c= n / V

Here, n= number of moles of solute dissolved in ‘V’ litre of the solution.

Therefore, π = n/V . RT or

Ï€V=nRT (9.32)

If the solution is prepared by dissolving wB g of nonvolatile solute in wA g of solvent, then the number of moles ‘n’ is,

n= wB/MB

Since,MB = molar mass of the solute

Substituting the ‘n’ in 9.32, we get,

From the equation 9.33, molar mass of the solute can be calculated.