Calculating The Molecular Weight Of Solute From Osmotic Pressure
π = iMRT
π – osmotic pressure (atm), i-Van’t Hoff factor, M –concentration of solution (moles/L), R-0.0821 atm.L/mol.K, T – temperature (K)
The degradation of cellulose produces cellobios, a sugar substance. If 250.0 mL of aqueous solution containing 12.00g of cellobios at 25.0˚C gives rise to an osmotic pressure of 503.5 mmHg. Calculate the molecular weight of cellobios.
Since the molecular weight of the substance is unknown. The mass of the solute con’t be calculated into moles.
Thus, we assume that the moles of solute are X moles.
Osmotic Pressure = 503.5/760 = 0.6625 atm
0.6625 atm = 1 x Xmole/.250L x 0.0821 atm L/molK x 298K