Practice question
Question
What is the molar mass of a solute if 5 g of it in 250 mL of solution produces an osmotic pressure of 0.984 atm at 27°C? ( R = 0.0821 L atm mol⁻¹ K⁻¹ )
Explanation
Pi = (w/M V) RT . 0.984 = (5/M × 0.25) × 0.0821 × 300 . M = (5 × 0.0821 × 300/0.984 × 0.25) ≈ 50 g/mol .