Which of the following aqueous solutions having same molality exhibits maximum boiling point elevation? (Assume complete dissociation)

The elevation of boiling point of $0.10 \ m$ aqueous $CrCl_{3} \cdot xNH_{3}$ solution is two times that of $0.05 \ m$ aqueous $CaCl_{2}$ solution. The value of $x$ is.........
[Assume $100 \%$ ionisation of the complex and $CaCl_{2},$ coordination number of $Cr$ as $6,$ and that all $NH_{3}$ molecules are present inside the coordination sphere $]$

If sodium sulphate is considered to be completely dissociated into cations and anions in aqueous solution,the change in freezing point of water $(\Delta T_f),$ when $0.01 \ mol$ of sodium sulphate is dissolved in $1 \ kg$ of water,is $(K_f = 1.86 \ K \ kg \ mol^{-1})$ (in $K$).

$0.6 \, mL$ of acetic acid $(CH_{3}COOH)$,having density $1.06 \, g \, mL^{-1}$,is dissolved in $1 \, L$ of water. The depression in freezing point observed for this strength of acid was $0.0205^{\circ} \, C$. Calculate the van't Hoff factor and the dissociation constant of acid.

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

The van't Hoff factor for $Ca(NO_3)_2$ is ...... .