Which of the following aqueous solutions should have the highest boiling point?

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,$K_{b}=0.512 \, K \, kg \, mol^{-1}$ ]

$A$ $0.5 \ m$ aqueous solution of a weak acid $(HX)$ is $20\%$ ionized. If $K_f$ for water is $1.86 \ K \ kg \ mol^{-1}$,the depression in freezing point of the solution is ....... $K$.

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 $]$

The freezing point of a $0.0020 \ m$ aqueous solution of $[CO(NH_3)_5(NO_2)]$ is $-0.00732 \ ^oC$. The number of ions produced (van't Hoff factor,$i$) when $1 \ mol$ of this ionic compound is dissolved in water is ..... $(K_f = 1.86 \ K \ kg \ mol^{-1})$

$17.4\%\, (w/v)$ $K_2SO_4$ $(Mw=174\, g/mol)$ solution at $27\, ^\circ C$ is isotonic to $4\%\, (w/v)\, NaOH$ solution at the same temperature. If $NaOH$ is $100\%$ ionized,what is the $\%$ ionization of $K_2SO_4$ in aqueous solution .......... $\%$.