Question

A solution of 1.8274g of a polypeptide in 274mL of a aqueous solution has an osmotic pressure at 31.40 degrees C of 2.012 mmHg. The approximate molecular weight of this polymer is _____ g/mol.

Answer 1

Answer: Hence, the approximate molecular weight of the poymer is 64106 g/mol

Explanation:

$\pi=CRT$

where,

$\pi$ = osmotic pressure of the solution = 2.012 mm Hg =  0.0026 atm

i = Van't hoff factor = 1 (for non-electrolytes)

Mass of solute (polypeptide) = 1.8274 g  

Volume of solution = 274 mL

R = Gas constant = $0.0821Latm/Kmol$

T = temperature of the solution = $31.40^0C=(273+31.40)K=304.4K$

Putting values in above equation, we get:

$0.0026=\frac{1.8274 g\times 1000}{M\times 274ml}\times 0.0821\times 304.4$

$M=64106g/mol$

Hence, the approximate molecular weight of the poymer is 64106 g/mol