Colligative Properties of Nonvolatile Solutes

Study Notes

Colligative Properties of Nonvolatile Solutes

Four main colligative properties: vapor pressure lowering, freezing point depression, boiling point elevation, and osmotic pressure.

Boiling Point Elevation

Defined as the difference between the boiling point of the solution (Tb) and the boiling point of the pure solvent (T°b): ∆Tb = Tb - T°b.
Directly proportional to the concentration of the solute, described by the formula: ∆Tb = Kb m, where Kb is the molal boiling-point elevation constant.

Freezing Point Depression

Defined as the difference between the freezing point of the pure solvent (T°f) and the freezing point of the solution (Tf): ∆Tf = T°f - Tf.
Also directly proportional to the concentration of the solute, shown by the equation: ∆Tf = Kf m, where Kf is the molal freezing-point depression constant.

Van't Hoff Factor (i)

Represents the number of ions produced from each molecule of a compound when it dissolves in a solution.
For dissociating compounds, the formulas for boiling point and freezing point become: ∆Tb = iKb m and ∆Tf = iKf m.

Osmosis

The process whereby solvent molecules pass through a semipermeable membrane from a less concentrated solution to a more concentrated one.

Osmotic Pressure

Defined as the pressure required to prevent osmosis from occurring.
Calculated using the formula: P = MRT, where P is osmotic pressure, M is molarity of the solute particles, R is the gas constant, and T is the temperature in Kelvin.

Types of Osmotic Solutions

Isosmotic solution: Has the same osmotic pressure as the solution inside a cell, resulting in no net water flow into or out of the cell.
Hyperosmotic solution: Exhibits higher osmotic pressure than the cell interior, causing water to move out of the cell, leading to cell shrinkage.
Hyposmotic solution: Shows lower osmotic pressure compared to the inside of the cell, causing water to enter the cell and resulting in cell swelling.

Description

This quiz covers the key concepts of colligative properties associated with nonvolatile solutes, including vapor pressure lowering, freezing point depression, boiling point elevation, and osmotic pressure. Each definition provides essential insights into how these properties are measured and calculated in solutions.