Answer:
- Effect: the vapor pressure of the liquid is lowered
- The vapor pressure of a solution is different from that of the pure solvent because of the presence of solute particles which compete with the solvent molecules on the surface of the liquid, thus reducing the number of solvent molecules that can reach the gaseous state.
Step-by-step explanation:
When a liquid in an enclosed system is left on standing, it begins to convert into its gaseous state (evaporates), and then goes back into its liquid state (condenses) on the surface of the system. This creates a pressure known as "vapor pressure", which can be increased by energy (heat in this case). As the liquid is heated, its vapor pressure increases until it gets to its boiling point.
With the introduction of a nonvolatile solute (a solute which does not evaporate) into this system, the solute particles competes with the solvent (liquid) on the surface of the solution, reducing the amount of solvent exposed for evaporation, thereby reducing the rate at which the liquid evaporates and condenses back into its liquid state. The presence of the solute therefore reduces the vapor pressure of the liquid.
Vapor pressure lowering is a colligative property (the property of a solution which is dependent on the concentration of solute molecules in a solution). The presence of a solute in a solution lowers the vapor pressure of a liquid and the extent to which the pressure is lowered, is determined by the concentration of the solute in the solution.