1. Vapor Pressure Lowering:
* The nonvolatile solute disrupts the solvent's ability to evaporate.
* The solute molecules occupy some of the surface area of the liquid, reducing the number of solvent molecules that can escape into the gas phase.
* This leads to a lowered vapor pressure of the solution compared to the pure solvent.
2. Boiling Point Elevation:
* Since the vapor pressure of the solution is lower, it takes a higher temperature to reach the boiling point (where vapor pressure equals atmospheric pressure).
* This is known as boiling point elevation, and the amount of elevation is proportional to the molality of the solute.
3. Freezing Point Depression:
* Adding a solute also disrupts the formation of the solvent's crystal lattice, making it harder for the solvent to freeze.
* This results in a lowered freezing point of the solution compared to the pure solvent.
* Again, the amount of depression is proportional to the molality of the solute.
4. Osmotic Pressure:
* Nonvolatile solutes create an osmotic pressure difference between the solution and a pure solvent.
* This pressure difference is proportional to the concentration of the solute.
Other effects:
* Viscosity: Nonvolatile solutes can increase the viscosity (resistance to flow) of the solvent.
* Surface Tension: The surface tension of the solvent can be affected, sometimes increased and sometimes decreased.
In summary:
Adding a nonvolatile solute to a solvent lowers the vapor pressure, raises the boiling point, lowers the freezing point, and creates osmotic pressure. It can also affect the viscosity and surface tension of the solvent. These effects are all related to the disruption of the solvent's molecular interactions caused by the solute.
