* Colligative Properties: The decrease in vapor pressure is a result of a colligative property called vapor pressure lowering. Colligative properties depend only on the number of solute particles in a solution, not their specific identity.
* Intermolecular Forces: NaCl dissolves in water, forming ions (Na+ and Cl-) in solution. These ions interact with water molecules through ion-dipole forces, which are stronger than the hydrogen bonding between water molecules themselves.
* Reduced Evaporation: This increased interaction between ions and water molecules makes it harder for water molecules to escape the liquid phase and enter the vapor phase (evaporation).
In simpler terms: The salt ions "hold onto" the water molecules more tightly, making it less likely for water to evaporate and lowering the vapor pressure.
Important Notes:
* The extent of vapor pressure lowering depends on the concentration of the salt solution. A higher concentration of salt leads to a greater decrease in vapor pressure.
* This principle is used in many applications, like salting roads in winter to lower the freezing point of water and prevent ice formation.
