Question

A 0.797 g sample of β‑galactosidase is dissolved in water to make 0.199 L of solution, and the osmotic pressure of the solution at 25 ∘C is found to be 0.853 mbar. Calculate the molecular mass of β‑galactosidase.

Answer 1

Answer:

Molecular mass of β‑galactosidase = 1.16*10^5g

Explanation:

The osmotic pressure (π) is related to the molarity (M) of a solution by the following equation:

$\Pi = i*M*R*T$

i = Von't hoff factor = 1 for non-electrolytes

R = gas constant = 0.0821Latm/mol-K

T = temperature

Based on the above equation, molarity of β‑galactosidase is:

$\M = \frac{\Pi}{iRT}=\frac{0.000842atm}{1*0.0821Latm/mol-K*(25+273)K)}= 3.44*10^{-5}mol/L$

$Moles\ galactosidase=molarity*volume= 3.44*10^{-5}moles/L*0.199L=6.85*10^{-6} moles\\\\Molar\ Mass\ galactosidase = \frac{mass}{moles} =\frac{0.797g}{6.85*10^{-6}mol } =1.16*10^{5} g$