Boiling Point Elevation Calculator

What is Boiling Point Elevation?

Boiling point elevation is a colligative property that describes the increase in the boiling point of a solvent when a solute is dissolved in it. When you add salt to water, the resulting solution boils at a higher temperature than pure water. This phenomenon occurs because the presence of solute particles reduces the vapor pressure of the solvent, requiring a higher temperature for the vapor pressure to reach atmospheric pressure.

The boiling point elevation depends only on the number of dissolved particles (concentration), not on their chemical identity. This makes it a colligative property, similar to freezing point depression and osmotic pressure.

The Boiling Point Elevation Formula

The boiling point elevation is calculated using the following equation:

$$\Delta T = i \cdot K_b \cdot m$$

Where:

• $\Delta T$ is the boiling point elevation (in °C)
• $i$ is the Van't Hoff factor (number of particles per formula unit)
• $K_b$ is the ebullioscopic constant of the solvent (in °C·kg/mol)
• $m$ is the molality of the solution (in mol/kg)

The boiling point of the solution is then:

$$T_{solution} = T_{solvent} + \Delta T$$

Ebullioscopic Constants of Common Solvents

Van't Hoff Factor

The Van't Hoff factor ($i$) accounts for the number of particles produced when a solute dissolves. For non-electrolytes like sugar, $i = 1$ because they do not dissociate. For strong electrolytes like sodium chloride (NaCl), $i \approx 2$ because each formula unit dissociates into two ions. For calcium chloride (CaCl₂), $i \approx 3$ as it produces three ions per formula unit.

For related boiling point tools, try the Boiling Point Calculator and the Boiling Point at Altitude Calculator.