Boiling Point Elevation Calculator

Dissolved solutes raise a solvent's boiling point.

How the Math Works

The boiling point elevation calculator uses the formula ΔTb = i · Kb · molality to determine how much a solute raises a liquid's boiling point. Here, ΔTb represents the change in boiling point temperature. The variable i is the van 't Hoff factor, indicating how many particles the solute dissociates into when dissolved (for example, NaCl has i=2 because it splits into Na+ and Cl- ions). Kb is the ebullioscopic constant specific to the solvent, a value that characterizes how strongly the solvent interacts with dissolved particles. Molality (m) measures the concentration of the solute in moles per kilogram of solvent, making this formula applicable to any amount of solution.

Practical Applications

To use this calculator, first identify your solvent and find its Kb value from reference tables. Next, determine the van 't Hoff factor for your solute based on its chemical properties and dissociation behavior. Calculate the molality by dividing the number of moles of solute by the mass of solvent in kilograms. Input these three values into the calculator, and the result will show you the temperature increase needed to boil your solution. For example, adding salt to water increases its boiling point by about 0.5 ‑1°C per 100g of NaCl dissolved in one liter of water.

Day-to-Day Use

Understanding boiling point elevation helps in everyday cooking and food preparation. When making homemade ice cream without an ice cream maker, knowing that adding salt to the ice‑water mixture lowers the freezing point (the reverse principle) helps achieve the right texture. In the kitchen, this knowledge explains why salting pasta water slightly raises its boiling point, potentially affecting cooking times. It's also useful for canning and preserving foods, where precise temperature control matters, and for outdoor cooking experiments like making rock candy or understanding why altitude affects cooking times as atmospheric pressure changes boiling points.

Worked example

NaCl (i=2), 1 m in water → +1.02 °C.

FAQ