Which solution has the highest vapor pressure? a. 20.0 g of glucose (C₆H₁₂O₆) in 100.0 mL of water b. 20.0 g of sucrose (C₁₂H₂₂O₁₁) in 100.0 mL of water c. 10.0 g of potassium acetate KC₂H₃O₂ in 100.0 mL of water

Key Concepts

Vapor Pressure

Vapor pressure is the pressure exerted by a vapor in equilibrium with its liquid or solid phase at a given temperature. It reflects the tendency of particles to escape from the liquid phase into the vapor phase. Solutions with lower concentrations of solute typically have higher vapor pressures because fewer solute particles disrupt the escape of solvent molecules.

Colligative Properties

Colligative properties are properties of solutions that depend on the number of solute particles in a given amount of solvent, rather than the identity of the solute. These properties include vapor pressure lowering, boiling point elevation, freezing point depression, and osmotic pressure. The more solute particles present, the greater the effect on the vapor pressure, leading to a lower vapor pressure for more concentrated solutions.

Molar Mass and Particle Count

The molar mass of a solute determines how many moles are present in a given mass of solute. For example, glucose (C6H12O6) has a lower molar mass than sucrose (C12H22O11), meaning that for the same mass, glucose will produce more moles of solute particles in solution. This difference in particle count affects the colligative properties, including vapor pressure, as more particles lead to a greater lowering of vapor pressure.