Which of the following lists the four colligative-property changes associated with high osmolality?

• A. Increased Boiling Point; Increased Osmotic Pressure; Decreased Vapor Pressure; Decreased Freezing Point
• B. Increased Boiling Point; Decreased Osmotic Pressure; Increased Vapor Pressure; Decreased Freezing Point
• C. Decreased Boiling Point; Increased Osmotic Pressure; Decreased Vapor Pressure; Increased Freezing Point
• D. Increased Boiling Point; Increased Osmotic Pressure; Increased Vapor Pressure; Decreased Freezing Point

Answer: (A)

High osmolality means there are more solute particles in solution, and colligative properties depend on particle number, not their identity. More particles raise the energy needed to vaporize enough to boil (boiling-point elevation) and disrupt crystal formation when freezing (freezing-point depression). They also reduce the tendency of solvent molecules to escape into the vapor (lower vapor pressure) and increase the tendency of solvent to move across a membrane (higher osmotic pressure).

So the four changes you’d expect are: boiling point increases, osmotic pressure increases, vapor pressure decreases, and freezing point decreases. That matches the option listing increased boiling point, increased osmotic pressure, decreased vapor pressure, and decreased freezing point.