Relative Lowering of Vapour Pressure

$$\frac{P^\circ - P}{P^\circ} = i \cdot x_{\text{solute}}$$

Concept: Colligative Property - Relates the fractional decrease in the vapour pressure of a solvent to the mole fraction of the dissolved non-volatile solute particles.

Notation:

• $$P^\circ$$ = Vapour pressure of pure solvent;
• $$P$$ = Vapour pressure of solution;
• $$i$$ = van 't Hoff factor;
• $$x_{\text{solute}}$$ = Mole fraction of solute.