Question

Which one of the following aqueous solutions will exhibit highest boiling point?

Options

• 0.01 M Na₂SO₄

• 0.01 M KNO₃

• 0.015 M urea

• 0.015 M glucose

Answer 1

0.01 M Na₂SO₄

Explanation:

Boiling point elevation is a colligative property and depends on

ΔT_b = i K_b m

Where i is the Van’t Hoff factor (number of particles in solution).

Na₂SO₄ dissociates into 3 ions = i = 3

KNO₃ dissociates into 2 ions = i = 2

Urea and glucose are non-electrolytes = i = 1

Despite having the same or lower molarity, Na₂SO₄ gives more particles, hence the highest boiling point elevation.