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

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The elevation in boiling point is a colligative property and is given by $Δ T_{b} = i \times K_{b} \times m$ .

For solutions with the same molality, $Δ T_{b} \propto i$ , where $i$ is the van't Hoff factor.

Assuming complete dissociation, the value of $i$ is equal to the number of ions produced per formula unit of the solute.

For KCl, $i = 2$ ( $K^{+}$ and $C l^{-}$ ).

For NaCl, $i = 2$ ( $N a^{+}$ and $C l^{-}$ ).

For $A lC l_{3}$ , $i = 4$ ( $A l^{3 +}$ and $3 C l^{-}$ ).

For $B a C l_{2}$ , $i = 3$ ( $B a^{2 +}$ and $2 C l^{-}$ ).

Since $A lC l_{3}$ produces the maximum number of ions, it has the highest van't Hoff factor and exhibits the maximum boiling point elevation.

Answer: $A lC l_{3}$

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