Which of the following compounds has a Van't Hoff factor $i$ equal to $2$ for a dilute solution?

Among the following $0.1 \ m$ aqueous solutions,which one will exhibit the lowest boiling point elevation,assuming complete ionization of the compound in solution?

$A$ solution containing $10 \ g$ of an electrolyte $AB_2$ in $100 \ g$ of water boils at $100.52^{\circ} C$. The degree of ionization of the electrolyte $(\alpha)$ is............ $\times 10^{-1}$.
(nearest integer)
[Given : Molar mass of $AB_2 = 200 \ g \ mol^{-1}$,$K_{b}$ (molal boiling point elevation constant of water) $= 0.52 \ K \ kg \ mol^{-1}$,boiling point of water $= 100^{\circ} C$;
$AB_2$ ionises as $AB_2 \rightarrow A^{2+} + 2B^{-}$]

Which of the following has the highest boiling point at $1 \, atm$ pressure?

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

The freezing point of a solution prepared by adding $8.1 \ g$ of $HBr$ ($90\%$ ionized) to $100 \ g$ of water is $...... \ ^\circ C$. (Given $K_f$ for water $= 1.86 \ K \ kg \ mol^{-1}$)