Dissolving a solute in a solvent raises the solvent's boiling point — this is why adding salt to pasta water technically raises its boiling point slightly.
Dissolving a solute in a solvent raises the solvent's boiling point — this is why adding salt to pasta water technically raises its boiling point slightly. The effect depends on the van't Hoff factor, the solvent's ebullioscopic constant, and the molality.
Dissolving salt (i=2) in water (Kb=0.512) at 0.5 mol/kg molality. ΔTb = 2 × 0.512 × 0.5 = 0.512°C — the solution boils at about 100.512°C instead of 100°C.
It's the increase in a solvent's boiling point caused by dissolving a solute in it — for example, salted water boils at a slightly higher temperature than pure water.
The temperature increase equals the van't Hoff factor times the solvent's ebullioscopic constant times the molality of the solution.
It explains why adding salt to water raises its boiling point slightly, and it's a classic method for determining a solute's molar mass in chemistry labs.