Which of the following $0.10 \mathrm{~m}$ aqueous solutions will have the lowest freezing point?
- $\mathrm{Al}_{2}\left(\mathrm{SO}_{4}ight)_{3}$
- $\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}$
- $\mathrm{KCl}$
- $\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}$
Solution
$\mathrm{Al}_{2}\left(\mathrm{SO}_{4}ight)_{3}$ provides five ions on ionisation
$\mathrm{Al}_{2}\left(\mathrm{SO}_{4}ight)_{3} \longrightarrow 2 \mathrm{Al}^{3+}+3 \mathrm{SO}_{4}^{2-}$
while KCl provides two ions
$\mathrm{KCl} ightleftharpoons \mathrm{K}^{+}+\mathrm{Cl}^{-}$
$\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}$ and $\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}$ are not ionised so they have
single particle. Hence, $\mathrm{Al}_{2}\left(\mathrm{SO}_{4}ight)_{3}$ have maximum value of depression in F.P or lowest F.P
Asked in: JEE-TOPICTESTS-CHEMISTRY