Question

0.6 g of a solute is dissolved in 0.1 L of a solvent which develops an osmotic pressure of 1.23 atm at 27°C. The molecular mass of the solute is ______.

Options

• 149.5 g/mol

• 120.15 g/mol

• 430 g/mol

• 112.32 g/mol

Answer 1

0.6 g of a solute is dissolved in 0.1 L of a solvent which develops an osmotic pressure of 1.23 atm at 27°C. The molecular mass of the solute is 120.15 g/mol.

Explanation:

van't Hoff's equation is

π = `"n"_2/"V" "RT"`

∴ π = `"W"/"M"_2 xx 1/"V" "RT"`

where, π = Osmotic pressure

W₂ = Weight of solute

M₂ = Molecular mass of solute

V = Volume of the solution

R = Ideal gas constant

T = Temperature

∴ 1.23 atm = `(0.6  "g")/"M"_2 xx 1/(0.1  "L") xx 0.0821  "L atm K"^-1  "mol"^-1 xx 300  "K"`

∴ M₂ = 120.15 g/mol