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

Calculate the freezing point (in ${}^{\circ}C$) of a solution obtained by dissolving $0.1 \ g$ of potassium ferricyanide (molecular weight $= 329$) in $100 \ g$ of water. Given that $K_f$ for water is $1.86 \ K \ kg \ mol^{-1}$.

$17.4\% \text{ (mass/volume) } K_2SO_4$ solution at $27^\circ C$ is isotonic to $5.85\% \text{ (mass/volume) } NaCl$ solution at $27^\circ C$. If $NaCl$ is $100\%$ ionized,what is the $\%$ ionization of $K_2SO_4$ in aqueous solution? [Atomic weights: $K = 39, Na = 23, S = 32, O = 16, Cl = 35.5$]

Which of the following is not a non-electrolyte?

At a certain temperature,the vapour pressure of pure water is $76 \ mm$ of $Hg$. When $1 \ mol$ of $Na_2SO_4$ is dissolved in $36 \ mL$ of water,the vapour pressure of the solution becomes $38 \ mm$ of $Hg$. What is the percentage dissociation of $Na_2SO_4$ in the solution?

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