Which method is used to measure the osmotic pressure of an aqueous solution?

$A$ $5\% \ (w/v)$ solution of anhydrous $CaCl_2$ at $0^o C$ exerts an osmotic pressure of $15 \ atm$. The degree of dissociation $(\alpha)$ of $CaCl_2$ is ....... $\%$.

$0.06 \% (w/v)$ aqueous solution of urea is isotonic with:

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 of the following solutions has the maximum osmotic pressure?

Calculate the osmotic pressure of a $0.2 \ M$ aqueous $KCl$ solution at $0^{\circ} C$ if the van't Hoff factor for $KCl$ is $1.83$. $[R = 0.082 \ dm^3 \ atm \ mol^{-1} \ K^{-1}]$ (in $atm$)