Boiling Point Elevation Calculator

Boiling point elevation is a colligative property: it depends primarily on the number of dissolved particles rather than their chemical identity. A nonvolatile solute lowers the solvent's vapor pressure. The solution therefore needs a higher temperature before its vapor pressure reaches the surrounding pressure and boiling begins. The difference between the solution boiling point and the pure solvent boiling point is the boiling point elevation. For a sufficiently dilute ideal solution, the elevation is calculated by multiplying molality, the solvent's ebullioscopic constant, and the Van't Hoff factor. Molality is moles of solute per kilogram of solvent, not per liter of solution. The ebullioscopic constant Kb is a property of the solvent and expresses how strongly one molal unit changes its boiling point. Water has a Kb of approximately 0.512 °C·kg/mol at ordinary pressure. Other solvents have different constants and pure boiling points. The Van't Hoff factor represents the effective number of dissolved particles produced by each formula unit. A nonelectrolyte such as glucose generally uses a factor near one because its molecules remain intact. An ideal sodium chloride solution uses a factor near two because it dissociates into sodium and chloride ions. Calcium chloride is often introduced with an ideal factor of three. Real electrolyte solutions may have lower effective factors because ions interact, especially as concentration increases. This calculator reports both the elevation and the estimated solution boiling point. It adds the elevation to the pure solvent value entered by the user. The simple relationship is most reliable for dilute solutions containing a nonvolatile solute. It does not account for solute volatility, association, strong nonideal interactions, pressure changes, or concentration changes during extended boiling. Use experimentally determined activity models for precision work with concentrated solutions. Boiling point elevation is useful in chemistry classes, molecular-mass experiments, formulation studies, and rough process estimates. It also helps explain familiar observations such as dissolved salts raising water's boiling point, although ordinary cooking concentrations generally produce a small increase. Careful units and a realistic Van't Hoff factor are essential for an internally consistent result.