Boiling Point Elevation

Boiling point elevation is a colligative property — it depends on how many dissolved particles are present, not on what those particles chemically are — and this calculator implements it directly as ΔTb = i × Kb × m, where i is the van't Hoff factor, Kb is the solvent's ebullioscopic constant, and m is molality (moles of solute per kilogram of solvent, not per liter of solution, which matters because molality doesn't shift with temperature the way molarity does). The default Kb of 0.512 °C·kg/mol is water's value; a different solvent needs its own Kb entered directly since the calculator has no built-in solvent database. The van't Hoff factor is where common mixups happen: it isn't the solute's formula weight or concentration, but the number of discrete particles each formula unit produces in solution — table sugar stays intact at i = 1, NaCl dissociates into two ions for i = 2, and CaCl₂ dissociates into three for i = 3. Getting this wrong is the single most common source of error when using this formula by hand.

New boiling point simply adds the calculated elevation to whatever normal boiling point you specify for the solvent (100 °C for water, but editable for other solvents under advanced options). The chart traces ΔTb against molality from zero up to whichever is larger — twice your entered value, or 5 mol/kg as a floor so low-molality solutions still get a readable curve rather than a nearly flat line — holding Kb and i fixed, so it shows the straight-line relationship colligative properties are known for — useful for reading off elevation at nearby concentrations without re-entering values one at a time. As with any ideal colligative-property model, this assumes complete dissociation and no ion-pairing at high concentration, which real electrolyte solutions increasingly violate as molality climbs.