Freezing Point Depression Calculator

Why solute lowers the freezing point

Dissolved particles interfere with the orderly formation of the solid solvent phase, so the solution must be cooled further before freezing begins. Like boiling point elevation, this is a colligative effect that depends primarily on particle count in dilute solution.

That is why the page emphasizes particle molality i × m alongside the observed freezing-point shift. More dissolved particles generally mean a larger depression below the pure-solvent freezing point.

Formula used here

This calculator uses the standard dilute-solution relation ΔTf = iKf m. Kf is the solvent's cryoscopic constant, m is molality, and i is the van't Hoff factor.

Worked example

For a 1.00 m nonelectrolyte in water, Kf = 1.86 °C·kg/mol and i ≈ 1, so the freezing point depression is 1.86 °C. The solution therefore freezes near -1.86 °C instead of 0 °C.

If an electrolyte contributes more dissolved particles, the shift is larger at the same formal molality. That is why ion-producing solutes are especially effective at depressing the freezing point.