Calculates how much a dissolved solute raises a solvent’s boiling point, a classic colligative property.
How it works
The number of particles the solute dissociates into is multiplied by the solvent’s ebullioscopic constant and the solution’s molality.
What this does not include
This does not include the opposite effect on freezing point — for that, use this site’s freezing point depression calculator instead, which uses the same underlying principle applied to the other phase transition.
How to use this calculator
- Enter the Van’t Hoff factor, the solvent’s ebullioscopic constant (water’s value is pre-filled), and the molality.
A worked example
A solute with van’t Hoff factor 2, Kb = 0.512, molality 0.5: boiling point elevation = i×Kb×m = 2×0.512×0.5 = 0.512°C.
A non-dissociating solute (i=1), Kb = 0.512, molality 2: elevation = 1.024°C.
What the variables mean
| Variable | Meaning |
|---|---|
| i (van’t Hoff factor) | Number of particles the solute dissociates into |
| Kb | The solvent’s boiling point elevation constant |
| Molality | Moles of solute per kg of solvent |
Edge cases worth knowing
This is the same underlying principle as freezing point depression, just in the opposite direction — dissolved particles disrupt phase transitions, raising boiling point the same way they lower freezing point.
A negative van’t Hoff factor has no physical meaning, so the calculator declines to show a result for one.
Frequently asked questions
What is the Van’t Hoff factor?
The number of particles a solute breaks into when dissolved — table salt (NaCl) splits into two ions, so it uses a factor of 2, while sugar doesn’t dissociate at all, using a factor of 1.
Why does adding salt to water raise its boiling point?
The dissolved particles interfere with water molecules escaping into vapor, requiring a higher temperature to reach the same vapor pressure needed for boiling.
Is boiling point elevation the same for any solute at the same molality?
Only if they dissociate into the same number of particles — a solute with a higher Van’t Hoff factor produces a proportionally larger boiling point elevation at the same molality.
