Bovine serum albumin (BSA) is a biochemically useful protein. A 0.400 g sample of bovine serum albumin is dissolved in water to make 0.179 L of solution

Question

the osmotic pressure of the solution at 25 ∘C is found to be 0.835 mbar. Calculate the molecular mass of bovine serum albumin

Answer 1

Osmotic pressure (π) = iMRK

π = 0.835 mbar = 0.000835 bar x 0.987 atm / bar = 8.24x10^-4 atm

i = vant Hoff factor = 1 for BSA

M = molarity = moles/L = ?

R = gas constant = 0.0821 Latm/Kmol

K = temperature in Kelvin = 25 + 273 = 298K

Solving for M, we have...

M = 8.24x10^-4 atm / (1)(0.0821 Latm/Kmol)(298K)

M = 3.37x10^-5 M

To fine the number of moles we have...

3.37x10^-5 mols / L x 0.179 L = 6.03x10^-6 moles of BSA

Molar mass = grams / moles = 0.400 g / 6.03x10^-6 moles

Molar mass = 66,338 g / mol

(be sure to check all of the math)