In which case is Raoult's law not applicable?

$0.2 \ molal$ aqueous solution of an electrolyte $A_3B$ is $90\%$ ionised. The boiling point of the solution at $1 \ atm$ is ........ $K.$ ($K_b$ for $H_2O = 0.52 \ K \ Kg \ mol^{-1}$ and $B.pt.$ of $H_2O = 373 \ K$)

$MX_{2}$ dissociates into $M^{2+}$ and $X^{-}$ ions in an aqueous solution,with a degree of dissociation $(\alpha)$ of $0.5$. The ratio of the observed depression of freezing point of the aqueous solution to the value of the depression of freezing point in the absence of ionic dissociation is

Molal depression constant for a solvent is $4.0 \, K \, kg \, mol^{-1}$. The depression in the freezing point of the solvent for $0.03 \, mol \, kg^{-1}$ solution of $K_2SO_4$ is .............. $K$ (Assume complete dissociation of the electrolyte).

The ratio of the value of any colligative property for a $KCl$ solution to that of a sugar solution of the same concentration is:

Which of the following solutes dissolved in water,having the same concentration,exhibits the highest value of colligative property?