Question

The osmotic pressure of 100.0 mL of a 25 C solution containing 0.50 g of a protein is 5.8 Torr. Based on this information, determine the molar mass of the protein in g/mol.
Hint: The protein does not dissociate in water; thus the Van't Hoff factor equals 1.

a) 1.6 x 10¹

b) 1.6 x 10³

c) 1.6 x 10⁴

Answer 1

Formula relating osmotic pr & vant Hoff factor is

= i CRT   - osmotic pr i- vant Hoff factor C= concentration of solution R- gas const T- temp = 25 C

T = 273+25= 298k R= 0.0821Latm/k/mol

   = 5.8 Torr 1atm = 760 torr 5.8/760= 0.0076atm

i= 1 C= n/V n - no: of moles of protein V - volume of solu in litres = 100ml = 0.1l   

n = w/m w - wt of protein in gms m- molar mass of protein   

m = w R T / V

= 0.50 x 0.0821x 298 / 0.0076 x 0.1

= 1.6 x 104 g/mol so molar mass of protein is

c) 1.6 x 104