Question

In a laboratory experiment, a student found that a 158-mL aqueous solution containing 2.059 g of a compound had an osmotic pressure of 16.9 mm Hg at 298 K. The compound was also found to be nonvolatile and a nonelectrolyte. What is the molar mass of this compound?

Answer 1

osmotic pressure = 16.9 mmHg = 0.02224 atm

temperature = 298 K

volume = 0.158 L

Osmotic pressure = M S T

0.02224 = M x 0.0821 x 298

M = 9.09 x 10^-4

Molarity = 9.09 x 10^-4 M

molarity = moles / volume

9.09 x 10^-4 = moles / .158

moles = 1.436 x 10^-4 mol

moles = mass/ molar mass

1.436 x 10^-4 = 2.059 / molar mass

molar mass = 1.434 x 10^4 g/mol