What is the compound's molar mass?

Question

When 3.14g of non-ionizing water soluble compound is dissolved in water to make a 250mL solution, the resulting solution has an osmotic pressure of 0.525 atm at 25 degrees C . What is the compound's molar mass?

Answer 1

Osmotic pressure (π) = iMRT

π = 0.525 atm

i = van't Hoff factor = 1 for a non-ionizing compound

M = molarity = moles solute / liter solution =?

R = constant = 0.0821 Latm/Kmol

T = temperature in K = 25ºC + 273 = 298K

Solving for M, we have ...

M = π / iRT = 0.525 / (1)(0.0821)(298)

M = 0.0215 M = 0.0215 moles/L

Since we have 250 ml, that's equal to 0.250 L

Moles = 0.0215 mols / L x 0.250 L = 0.005375 moles

molar mass = g/mol

molar mass = 3.14 g / 0.005375 mols

molar mass = 584 g/mol