VAPOR PRESSURE LOWERING
Adding non-volatile solute to volatile solvent lowers the solvent’s vapor pressure. For example, water normally boils at 100 degrees C (212 F) but if you add something like salt to the solution, it decreases the vapor pressure of the solution.
- The water will only boil if it’s vapor pressure is equal to atmospheric pressure. Thus you would need to heat the water to a higher temperature.
- The vapor pressure lowering is a colligative property. Colligative property refers to the ratio of solute particles to solvent, and not the identity of the solute (identity which means the type of solute).