The van't Hoff factor $(i)$ for a dilute aqueous solution of the strong electrolyte barium hydroxide is

The osmotic pressure of a $0.1 \ M$ solution of $NaCl$ and $Na_2SO_4$ will be:

$80$ mole percent of $MgCl_2$ is dissociated in aqueous solution. The vapour pressure of $1.0$ molal aqueous solution of $MgCl_2$ at $38^{\circ} C$ is $.........$ $mm$ $Hg$. (Nearest integer)
Given : Vapour pressure of water at $38^{\circ} C$ is $50$ $mm$ $Hg$.

For $0.01 \ M$ solutions of urea,$NaCl$,and $Na_2SO_4$,the ratio of their depression in freezing point is .......

The freezing point (in ${}^{\circ}C$) of a solution containing $0.1 \ g$ of $K_3[Fe(CN)_6]$ (Mol. Wt. $329$) in $100 \ g$ of water $(K_f = 1.86 \ K \ kg \ mol^{-1})$ is

For the dissociation of $Na_2SO_4$,how is the degree of dissociation $\alpha$ used to calculate the van't Hoff factor $(i)$?