Vapour pressure lowering is a colligative property, which means it depends on the number of solute particles in a solution and not on their identity. When a non-volatile solute is added to a solvent, the solvent's vapour pressure decreases. This happens because the solute particles occupy space at the surface of the liquid, preventing some solvent molecules from evaporating into the gas phase.
This effect can be understood using Raoult's Law, which states that the vapour pressure of a solution is directly proportional to the mole fraction of the solvent. So, the more solute particles present, the lower the mole fraction of the solvent and, consequently, the lower the vapour pressure.
- The more particles present in the solution, the more the vapour pressure is lowered.
- This property is independent of the type of particles, focusing only on the quantity.