0.102 g of an unknown (non electrolyte) compound is dissolved in enough water to make 100. mL of a solution and has an osmotic pressure of 28.1 mmHg at 20 C. Calculate the molar mass of the compound.

680 g/m is the molar mass for the unknown, non electrolyte, compound.

Explanation:

Let's apply the formula for osmotic pressure

π = Molarity. R. T

T = T° absolute (in K)

R = Universal constant gases

π = Pressure

Molarity = mol/L

As units of R are L. atm/mol. K, we have to convert the mmHg to atm

760 mmHg is 1 atm

28.1 mmHg is (28.1.1) / 760 = 0.0369 atm

0.0369 atm = M. 0.082 L. atm/mol. K. 293K

(0.0369 atm / 0.082 mol. K/L. atm. 293K) = M

0.0015 mol/L = Molarity

This data means the mol of solute in 1L, but we have 100mL so

Molarity. volume = mol

0.0015 mol/L. 0.1L = 1.5x10⁻⁴ mole

The molar mass will be: 0.102g / 1.5x10⁻⁴ m = 680 g/m