Boiling-Point Elevation Calculator
Enter the van't Hoff factor i, ebullioscopic constant Kb, molality b, and pure-solvent boiling point to compute the boiling-point elevation ΔTb = i·Kb·b and the solution boiling point.
Input Data
Results
At a glance:Enter the van't Hoff factor i, ebullioscopic constant Kb, molality b, and pure-solvent boiling point to compute the boiling-point elevation ΔTb = i·Kb·b and the solution boiling point.
Formula
ΔTb = i · Kb · b.
Solution boiling point = pure-solvent boiling point + ΔTb.
$$\Delta T_b = i \, K_b \, b$$How to Use
- Enter the van't Hoff factor i, ebullioscopic constant Kb, and molality b.
- Enter the pure-solvent boiling point.
- The calculator returns ΔTb and the solution boiling point.
FAQ
What are colligative properties?
Colligative properties depend only on the number of solute particles, not their identity. They include boiling-point elevation, freezing-point depression, vapor-pressure lowering, and osmotic pressure. Boiling-point elevation is one of them.
How are boiling-point elevation and freezing-point depression related?
They are two sides of the same mechanism (the solute lowers the solvent's chemical potential and vapor pressure): adding solute raises the boiling point and lowers the freezing point, widening the liquid range at both ends. But because water's Kb (0.512) is far smaller than its Kf (1.86), the boiling-point rise is much smaller than the freezing-point drop at the same concentration.
Does adding salt to cooking water really raise the temperature noticeably?
In theory yes, but household salt amounts give a very low molality and a rise usually under 1 °C, which has almost no effect on cooking time. The main purpose of adding salt is seasoning, not heating.
What is the van't Hoff factor i?
i is the number of particles a solute unit dissociates into in solution. Non-electrolytes (sucrose, glucose) do not dissociate, i = 1; NaCl dissociates into 2 ions, i ≈ 2; CaCl₂ into 3 ions, i ≈ 3. More particles mean a stronger colligative effect.
Why use molality instead of molarity for concentration?
Because colligative-property formulas need a temperature-independent concentration, and molality (mol/kg) is based on solvent mass and does not change with temperature — the best fit. Molarity (mol/L) changes with thermal expansion and contraction of the solution volume.
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References
Content review: Calculatorism Science Team. Results are for reference only; please refer to the relevant authorities for the official figures.