Which statement about boiling point elevation is true?

Which statement about boiling point elevation is true?

• A. It decreases the boiling point of the solvent
• B. It is independent of the number of dissolved particles
• C. It depends on the solvent's color
• D. It is described by ΔTb = i Kb m

Answer: (D)

Boiling point elevation is a colligative property: the rise in boiling temperature depends on how many dissolved particles are present, not on what those particles are. When a nonvolatile solute is added, the solvent’s vapor pressure drops, so the liquid must reach a higher temperature to boil. The relationship is given by ΔTb = i Kb m, where ΔTb is the boiling point rise, i is the van’t Hoff factor (the number of particles the solute yields in solution, adjusted for any incomplete dissociation), Kb is a solvent-specific constant, and m is the molality of the solute. So increasing the number of dissolved particles increases ΔTb. The color of the solvent has no role here, and the boiling point change depends on particle concentration, not on the particles’ identity. That’s why the statement carrying the equation ΔTb = i Kb m is the true description.

Boiling point elevation is a colligative property: the rise in boiling temperature depends on how many dissolved particles are present, not on what those particles are. When a nonvolatile solute is added, the solvent’s vapor pressure drops, so the liquid must reach a higher temperature to boil. The relationship is given by ΔTb = i Kb m, where ΔTb is the boiling point rise, i is the van’t Hoff factor (the number of particles the solute yields in solution, adjusted for any incomplete dissociation), Kb is a solvent-specific constant, and m is the molality of the solute. So increasing the number of dissolved particles increases ΔTb.

The color of the solvent has no role here, and the boiling point change depends on particle concentration, not on the particles’ identity. That’s why the statement carrying the equation ΔTb = i Kb m is the true description.