Raoult's Law Calculator
Calculator
\[ P_{\text{solution}} = \sum_i x_i P_i^* \qquad x_i = \frac{n_i}{\sum_j n_j} \]
xi = mole fraction of component i, P*i = pure vapour pressure of component i. Colligative properties use solute mole fraction and solvent constants.
Vapour Pressure of Solution

Enter moles and pure vapour pressure for each component. At least 2 components required.

Component Moles (mol) P* (kPa)
Boiling Point Elevation
\[ \Delta T_b = K_b \cdot m \cdot i \]
Freezing Point Depression
\[ \Delta T_f = K_f \cdot m \cdot i \]
About This Tool

Raoult's Law states that the partial vapour pressure of each component in an ideal solution equals its mole fraction multiplied by its pure-component vapour pressure: Pᵢ = xᵢ · P*ᵢ. The total vapour pressure of the mixture is the sum of all partial pressures. This calculator accepts any number of components — enter the moles and pure vapour pressure (in kPa) for each, and the tool computes mole fractions and the total solution vapour pressure automatically. The colligative properties sections cover boiling point elevation (ΔTb = Kb · m · i) and freezing point depression (ΔTf = Kf · m · i), where Kb and Kf are the ebullioscopic and cryoscopic constants of the solvent, m is the molality of the solution, and i is the van't Hoff factor accounting for ionic dissociation. Water constants (Kb = 0.512 °C·kg/mol, Kf = 1.86 °C·kg/mol) are pre-filled but can be changed for any solvent.