Which of the following aqueous solution will exhibit highest boiling point?

Question

Question

This question was previously asked in

NEET 2025 Official Paper (Held On: 04 May, 2025)

Answer 1

CONCEPT:

Elevation in Boiling Point

The boiling point of a solution increases when a non-volatile solute is added to it. This phenomenon is known as elevation in boiling point.
The elevation in boiling point (ΔTb) is directly proportional to the molality of the solution and the van 't Hoff factor (i), given by:
ΔTb = i × Kb × m
Here:
- i = Van 't Hoff factor (number of particles the solute dissociates into).
- Kb = Boiling point elevation constant.
- m = Molality of the solution.

EXPLANATION:

Van 't Hoff factors for the given solutes:
- Urea (0.01 M): Does not dissociate, i = 1.
- KNO₃ (0.01 M): Dissociates into K⁺ and NO₃⁻, i = 2.
- Na₂SO₄ (0.01 M): Dissociates into 2 Na⁺ and SO₄²⁻, i = 3.
- C₆H₁₂O₆ (0.015 M): Does not dissociate, i = 1.
Based on the formula ΔTb = i × Kb × m:
- Higher i leads to a greater elevation in boiling point.
- Na₂SO₄ (i = 3) will exhibit the highest boiling point among the solutions.

Therefore, the solution with 0.01 M Na₂SO₄ will exhibit the highest boiling point.