The properties which depend on the number of solute particles irrespective of their nature relative to the total numbers of particles in the solution are called colligative properties. These are relative lowering of vapour pressure of the solvent, depression of freezing point of the solvent, elevation of boiling point of the solvent and osmotic pressure of the solution. All of these properties help in calculating the observed molar mass of the solute. Determination of osmotic pressure is considered best for the determination of molecular mass of the solute.
Which solution has the highest boiling point ?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 2 m glucose
The elevation of boiling point is a colligative property: it depends only on the number of solute particles, not on their nature.
\( \displaystyle \Delta T_b = i\,K_b\,m \)
Glucose is a non-electrolyte: it does not dissociate, so i = 1 for every option. With the same solvent (same Kb), ΔTb is proportional to the molality alone. The highest molality, 2 m, gives the largest elevation and so the highest boiling point:
\( \displaystyle \Delta T_b:\ 0.1K_b \lt 0.5K_b \lt 1K_b \lt 2K_b \)
NCERT (2026-27 edition):
Elevation of Boiling Point – “… Similar to lowering of vapour pressure, the elevation of boiling point also depends on the number of solute molecules rather than their nature. A solution of 1 mol of sucrose in 1000 g of water boils at 373.52 K at one atmospheric pressure.”