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Chemistry

Boiling point elevation calculator

How much a solvent’s boiling point rises when a solute is dissolved in it (a colligative property).

What this calculator does

Boiling point elevation works out how much a solvent’s boiling point rises when a solute is dissolved in it (a colligative property). Enter your own figures above and the answer updates as you type: nothing is fixed in the code, so the result reflects exactly the numbers you supply.

The formula this calculator evaluates is printed under the tool and explained below, so you can check the working by hand or reuse it in a spreadsheet.

The formula

FormulaΔTb = i·Kb·m, m = moles solute / kg solvent

The inputs explained

FieldWhat to enter
Mass of solute (g)A number, measured in g. Starts at 10.
Molar mass of solute (g/mol)A number, measured in g/mol. Starts at 58.44.
Mass of solvent (kg)A number, measured in kg. Starts at 1.
Ebullioscopic constant Kb (water 0.512) (°C·kg/mol)A number, measured in °C·kg/mol. Starts at 0.512.
Van’t Hoff factor iA number. Starts at 1.
Boiling point of pure solvent (°C)A number, measured in °C. Starts at 100.

Worked examples

Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.

How the answer changes with mass of solute

Every other input is held at the calculator’s starting values while mass of solute varies. Select any row to load that scenario into the calculator.

How the answer changes with mass of solute
Mass of solute (g)New boiling pointBoiling point elevation ΔTbMolality
5100.04 °C0.044 °C0.0856 mol/kg
7.5100.07 °C0.066 °C0.1283 mol/kg
10100.09 °C0.088 °C0.1711 mol/kg
15100.13 °C0.131 °C0.2567 mol/kg
20100.18 °C0.175 °C0.3422 mol/kg
30100.26 °C0.263 °C0.5133 mol/kg