Question

Which of the following aqueous solution should have highest boiling point?

• A. $1.0MNaOH$
• B. $1.0MN{a}_{2}S{O}_4$
• C. $1.0MN{H}_{4}N{O}_3$
• D. $1.0MKN{O}_3$

Answer 1

The correct option is B $1.0MN{a}_{2}S{O}_4$

More the value of van't Hoff factor (i), more is the boiling point.

For most of the ionic compounds dissolved in water, the van't Hoff factor is equal to the number of discrete ions in a formula unit of the substance.

$NaOH⟶N{a}^{+}+O{H}^{-}$ $i=2$

$N{a}_{2}S{O}_4⟶2N{a}^{+}+{S{O}_4}^{2-}$ $i=3$

$N{H}_{4}N{O}_3⟶{N{H}_4}^{+}+{N{O}_3}^{-}$ $i=2$

$KN{O}_3⟶K^{+}+{N{O}_3}^{-}$ $i=2$

$\because i$ is maximum for $N{a}_{2}S{O}_4(=3)$, it has a maximum boiling point.

Hence, option B is correct.