Boiling Point Elevation Calculator
Dissolving a solute in a solvent raises its boiling point above the pure solvent's — this calculates exactly how much, based on the solute's concentration and how many particles it actually breaks into when dissolved.
Inputs
Result
+0.512 °C
Water would boil at 100.512 °C
How it works
ΔTb = i·Kb·m
How the boiling point elevation calculator works
ΔTb = i × Kb × m, where i is the van 't Hoff factor (particles produced per formula unit dissolved), Kb is the solvent's specific ebullioscopic constant, and m is molality.
Worked example: van 't Hoff factor 2, Kb 0.512 °C·kg/mol, molality 0.5 mol/kg
- ΔTb = 2 × 0.512 × 0.5 = 0.512°C.
- For water (normal boiling point 100°C): new boiling point = 100 + 0.512 = 100.512°C.
Common mistakes to avoid
Using a van 't Hoff factor of 1 for a solute that actually dissociates into multiple ions
A non-dissociating molecular solute (like sugar) has i = 1, but an ionic compound that fully dissociates (like a salt splitting into two ions) has i = 2 or higher — using the wrong factor for an ionic compound significantly understates the actual boiling point elevation.
Applying water's Kb value to a different solvent
Kb is specific to each solvent, not a universal constant — using water's commonly cited 0.512 °C·kg/mol for a calculation actually involving a different solvent (which has its own distinct Kb value) produces an incorrect result.
Frequently asked questions
Why does dissolving something in a liquid raise its boiling point at all?
Dissolved solute particles interfere with solvent molecules' ability to escape into vapour, effectively requiring a higher temperature to reach the same vapour pressure needed for boiling — this is a colligative property, depending on how many dissolved particles are present, not on what specific substance they are.
What does the van 't Hoff factor actually represent?
It's the number of individual particles one formula unit of solute produces upon dissolving — a non-ionic molecular compound typically has i=1 (it stays as one particle), while an ionic compound that fully dissociates into multiple ions has a correspondingly higher i value.
Why is this called a 'colligative' property?
Colligative properties depend on the number of dissolved particles present, not on their chemical identity — boiling point elevation, freezing point depression, and osmotic pressure are all colligative properties governed by this same particle-counting principle.
How is this related to the Molality Calculator?
Molality is a required input for this calculation — the Molality Calculator would typically be used first to find that value from moles of solute and solvent mass, before applying it here to find the boiling point elevation.
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