Which of the following salts has the same value of Van't Hoff factor $i$ as that of $K_4[Fe(CN)_6]$?

The elevation in boiling point of a solution of $10 \ g$ of a binary electrolyte (of molecular mass $100$) in $100 \ g$ of water is $\Delta T_b$. Then,the value of $K_b$ for water is

Calculate the depression in the freezing point of a solution containing $0.1 \ g$ of $K_3[Fe(CN)_6]$ in $100 \ g$ of $H_2O$. (Molecular weight of $K_3[Fe(CN)_6] = 329 \ g \ mol^{-1}$; $K_f = 1.86 \ K \ kg \ mol^{-1}$)

In an aqueous solution of potassium ferrocyanide,the degree of dissociation of the salt is $80\%$. The value of the van't Hoff factor is:

$A$ 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 aqueous solutions exhibits the minimum freezing point depression upon complete dissociation?