Which inorganic precipitate acts as a semipermeable membrane,or what is the chemical composition of a semipermeable membrane?

$A$ solution containing $8.6 \ g$ of urea per liter is isotonic with a $0.5\% \ (w/v)$ solution of a non-volatile organic solute. What is the molar mass of the organic solute?

Osmotic pressure of a solution can be measured quickly and accurately by

Assuming the compounds to be completely dissociated in aqueous solution, identify the pair of the solutions that can be expected to be isotonic at the same temperature.

Which colligative property is most suitable for the determination of the molar mass of polymers?

At $27^{\circ} C$,the osmotic pressure of a solution containing $4 \ g$ of a non-electrolyte solute in $1.0 \ L$ of solution is $0.4 \ bar$. The molar mass of the solute in $g \ mol^{-1}$ is :
$(R=0.083 \ L \ bar \ K^{-1} \ mol^{-1})$