Colligative Properties and Solutions

These flashcards cover the key concepts related to deviations from Raoult's law, freezing point depression, boiling point elevation, osmotic pressure, and the Van’t Hoff factor, which are critical for understanding colligative properties in solutions.

What is Raoult’s Law in the context of ideal solutions?

In ideal solutions, the formation of solute-solvent interactions are equal to the solute-solute and solvent-solvent interactions.

What happens when solute-solvent interactions are stronger than solute-solute and solvent-solvent interactions?

The total vapor pressure of the solution will be less than predicted by Raoult’s law.

What occurs when solute-solvent interactions are weaker than solute-solute and solvent-solvent?

The total vapor pressure of the solution will be more than predicted by Raoult’s law.

How do the freezing and boiling points of a solution compare to those of the pure solvent?

The freezing point of a solution is lower and the boiling point is higher compared to the pure solvent.

What is the formula for calculating freezing point depression?

ΔTf = m Kf, where ΔTf is the change in freezing point, m is the molality, and Kf is the freezing point depression constant.

What is the freezing point depression constant for water?

Kf = 1.86 °C/m.

How do you calculate boiling point elevation?

ΔTb = m Kb, where ΔTb is the change in boiling point, m is the molality, and Kb is the boiling point elevation constant.

What is the osmotic pressure of a solution?

Osmotic pressure is the external pressure needed to stop the osmotic flow of water through a semipermeable membrane.

What is the Van’t Hoff Factor (i)?

The ratio of moles of solute particles in solution to moles of formula units dissolved.

What affects the Van’t Hoff Factor measured value compared to the theoretical value?

Ion pairing in solution often causes the measured van’t Hoff factor to be smaller than the theoretical value.

What is the relationship between osmotic pressure (Π) and solute concentration?

The osmotic pressure is directly proportional to the molarity of the particles: Π = MRT.

In a 0.10 m sodium chloride solution, how does the Van’t Hoff factor affect freezing point depression?

Since sodium chloride dissociates into nearly 2 mol ions, the Van’t Hoff factor for NaCl is approximately 2.

How does one compare boiling points of varying solutions?

The boiling point of a solution is impacted by the total concentration of ions, not just the mol concentration of the solute.