Boiling Point Elevation Calculator

Calculate boiling point elevation using delta Tb = Kb * m * i. Find new boiling point of solution with any solute. Includes van't Hoff factor for ionic compounds.

🌡️ Colligative📐 ΔTb = Kb·m·i🧪 Chemistry
Molality m (mol solute/kg solvent)
Kb of solvent (°C·kg/mol)
van't Hoff factor i
Normal boiling point T° (°C)
Please enter valid values.

Formula & Reference

VariableSymbolFormulaUnits
Boiling Point Elevation Calculator—ΔTb = Kb·m·i°C

Step-by-Step Examples

Example 1
NaCl in Water

0.500 mol/kg NaCl (i=2) in water (Kb=0.512 C-kg/mol).

  • dTb = 0.512 x 0.500 x 2 = 0.512 C
  • New boiling point: 100.00 + 0.512 = 100.512 C
✓ Tb = 100.51 C
Example 2
Glucose in Water

1.00 mol/kg glucose (i=1) in water.

  • dTb = 0.512 x 1.00 x 1 = 0.512 C
  • Glucose is non-electrolyte, i=1
✓ Tb = 100.51 C
Example 3
CaCl2 in Water

0.200 mol/kg CaCl2 (i=3) in water.

  • dTb = 0.512 x 0.200 x 3 = 0.307 C
  • CaCl2 gives 3 ions: Ca^2+ + 2Cl^-
✓ Tb = 100.31 C

Real-World Applications

🍳
Cooking
Dissolving salt or sugar in water slightly raises boiling point. Effect is small at culinary concentrations.
🧪
Antifreeze
Ethylene glycol raises boiling point and lowers freezing point of engine coolant.
💊
Pharmaceutical
Boiling point elevation affects drug formulation and sterilization temperature.
🏭
Industrial Evaporation
Sugar refining: concentrated sugar syrup has higher boiling point than pure water.

Common Mistakes to Avoid

⚠️
van't Hoff factor i

i=1 for non-electrolytes. i=2 for NaCl, HCl, KNO3. i=3 for CaCl2, MgSO4 (if fully dissociated). Actual i < theoretical due to ion pairing.

⚠️
Molality not molarity

Colligative properties use molality (mol/kg solvent), not molarity (mol/L solution). Molality is temperature-independent.

⚠️
Kb for common solvents

Water: 0.512 C-kg/mol. Benzene: 2.53. Cyclohexane: 2.79. Camphor: 5.61 C-kg/mol.

Frequently Asked Questions

What are colligative properties? ▾
Properties that depend on number of solute particles, not their identity: boiling point elevation, freezing point depression, osmotic pressure, vapor pressure lowering.
Why do solutes raise the boiling point? ▾
Dissolved particles reduce vapor pressure (Raoult law). Lower vapor pressure means higher temperature needed to reach atmospheric pressure (boiling point).
What is the van't Hoff factor? ▾
Number of particles per formula unit in solution. NaCl: 2 (Na+ and Cl-). CaCl2: 3 (Ca^2+ and 2Cl-). Glucose: 1 (does not dissociate). Actual i slightly less due to ion pairing.
How large is the boiling point elevation in practice? ▾
Small. 1 mol/kg NaCl in water: only 1.024 C elevation. Effect is proportional to m and i.
What is ebullioscopy? ▾
Measurement of molar mass from boiling point elevation: M = (Kb x mass_solute)/(dTb x mass_solvent). Useful for determining molar mass of unknown solutes.

Related Chemistry Calculators

🧊 Freezing Point Depression💧 Osmotic Pressure💧 Raoult Law🧪 Molality⚗️ All Colligative Props

Formula Explorer connections

Interpretation: This formula connects solute amount and solution volume, mass or particle count to concentration and colligative behavior. Assumption: Distinguish solution volume from solvent volume, use the stated temperature, and account for dissociation or nonideal activity when required.

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