Compute the boiling point elevation of a solution from ΔTb = Kb·m·i (molality × ebullioscopic constant × van ’t Hoff factor).
| Item | Formula / Note | Source / Standard |
|---|---|---|
| Boiling point elevation | ΔT_b = K_b · m · i, with K_b the ebullioscopic constant, m the molality and i the van't Hoff factor | Atkins PW, de Paula J, Physical Chemistry, Oxford Univ. Press |
| Colligative property | Elevation depends only on the number of solute particles, not their identity | IUPAC, Compendium of Chemical Terminology (Gold Book) |
| van't Hoff factor | i is the ratio of actual particles to formula units after dissociation | van't Hoff JH (1887), Die Rolle des osmotischen Druckes |
| Conditions | Valid for dilute solutions; non-ideality matters at higher concentration | Atkins PW, de Paula J, Physical Chemistry |
Boiling-point elevation and freezing-point depression constants for common solvents, with sources
| Solvent | Ebullioscopic constant K_b | Cryoscopic constant K_f | Source |
|---|---|---|---|
| Water | 0.512 | 1.86 | CRC Handbook / IUPAC (page default K_b = 0.512) |
| Benzene | 2.53 | 5.12 | CRC Handbook |
| Ethanol | 1.22 | 1.99 | CRC Handbook |
| Standard atmosphere | (boiling points referenced to 101 325 Pa) | — | ISO 2533 defining value (exact) |
Note: ΔT = K·m·i is a colligative dilute-solution approximation; for electrolytes the van 't Hoff factor i counts the ions but is smaller than the ideal value because of ion pairing, and deviations grow at higher concentration.