Which one of the following $0.10 \ M$ aqueous solutions will exhibit the largest freezing point depression?

If the $O.P.$ (Osmotic Pressure) of $1 \ M$ solutions of the following compounds in water can be measured,which one will show the maximum $O.P.$?

The boiling point (in ${}^{\circ}C$) of $0.1 \, molal$ aqueous solution of $CuSO_{4} \cdot 5H_{2}O$ at $1 \, bar$ is closest to $.....$
[Given : Ebullioscopic (molal boiling point elevation) constant of water,$K_{b}=0.512 \, K \, kg \, mol^{-1}$ ]

$19.5 \ g$ of $CH_2FCOOH$ is dissolved in $500 \ g$ of water. The depression in the freezing point of water observed is $1.0 \ ^\circ C$. Calculate the van't Hoff factor and dissociation constant of fluoroacetic acid.

$A$ solution containing $0.85 \ g$ of $ZnCl_2$ in $125.0 \ g$ of water freezes at $-0.23 \ ^\circ C$. The apparent degree of dissociation of the salt is ($K_f$ for water $= 1.86 \ K \ kg \ mol^{-1}$,atomic mass: $Zn = 65.3$ and $Cl = 35.5$)

The osmotic pressure of a dilute solution of an ionic compound $XY$ in water is four times that of a solution of $0.01\, M\, BaCl_2$ in water. Assuming complete dissociation of the given ionic compounds in water,the concentration of $XY$ (in $mol\, L^{-1}$) in solution is