# Find molar mass of solute using Π =MRT equation

Calculate the molarity, M, of the solution:

M = Π ÷ RT

Π = 1.78 x 10^{-3} atm

R = 0.0821 L atm K^{-1}mol^{-1}

T = 25^{o}C = 25 + 273 = 298K

M = 1.78 x 10^{-3} ÷ 0.0821 x 298 = 7.28 x 10^{-5}mol/L

Calculate the moles, n, of hemoglobin present in solution:

n = M x V

M = 7.28 x 10^{-5}mol/L

V = 100.0mL = 100.0 x 10^{-3}L

n = 7.28 x 10^{-5} x 100.0 x 10^{-3} = 7.28 x 10^{-6}mol

Calculate the molecular mass, MM, of the hemoglobin:

MM = mass ÷ n

mass = 0.500g

n = 7.28 ÷ 10^{-6}mol

MM = 0.500 ÷ 7.28 x 10^{-6} = 68,681 g/mol

Question:

0.500g hemoglobin was dissolved in enough water to make 100.0mL of solution.At 25^{o}C the osmotic pressure was found to be 1.78 x 10^{-3} atm.Calculate the molecular mass (formula weight) of the hemoglobin.