Physical Properties of Solutions (Chapter 13)

Vocabulary flashcards covering key terms and definitions from the lecture notes on physical properties of solutions, colligative properties, electrolytes, and colloids.

Raoult's Law

The partial pressure of a solvent over a solution equals the vapor pressure of the pure solvent multiplied by the mole fraction of the solvent in the solution (P1 = P° × χ1).

Mole fraction

The ratio of moles of a component to the total moles in a solution (χ1 = n1/(n1+n2)); used in Raoult's Law.

Vapor-pressure lowering

The decrease in a solvent's vapor pressure upon dissolving a nonvolatile solute; ΔP = P° − P_solution = χ2 × P° (or equivalently ΔP = χ2 P°1 for solvent 1).

Ideal solution

A solution that obeys Raoult's Law, where P_solution = χ1 P°1.

Boiling-point elevation

The increase in boiling point of a solution relative to the pure solvent; ΔTb = Kb × m, where m is molality.

Freezing-point depression

The decrease in freezing point of the solvent; ΔTf = Kf × m.

Osmotic pressure

The pressure required to stop osmosis; π = i × M × R × T, where i is the van't Hoff factor, M is molarity, R is 0.08206 L·atm/mol·K, and T is in K.

van't Hoff factor (i)

The ratio of the actual number of particles in solution after dissolution to the number of formula units initially dissolved.

Electrolyte

A substance that dissociates into ions in solution; strong electrolytes dissociate completely, weak electrolytes only partially.

Nonelectrolyte

A substance that dissolves in a solvent but does not dissociate into ions (i = 1).

Ion pair

A bound state of cations and anions in solution that reduces the number of free particles.

Colloid

A dispersion of particles (roughly 1–1000 nm) throughout another substance; exhibits the Tyndall effect and does not settle readily.

Tyndall effect

The scattering of light by colloidal particles, making a beam visible in a colloid.

Aerosol

A colloid with a dispersed phase in a gas (e.g., fog, smoke).

Foam

A colloid where a gas is dispersed in a liquid.

Emulsion

A colloid where a liquid is dispersed in another immiscible liquid.

Sol

A colloid in which a solid is dispersed in a liquid.

Gel

A colloid in which a liquid is dispersed in a solid.

Hydrophilic

Colloid surfaces with water-loving groups that stabilize particles in water.

Hydrophobic

Colloid surfaces that repel water; stabilization often requires surface modifications or surfactants.

Emulsification

The process of stabilizing a dispersed colloid that would otherwise separate.

Surfactant

A compound with both a hydrophilic head and a hydrophobic tail that stabilizes emulsions (e.g., sodium stearate).

Colloids categories (general)

Categories include aerosols, foams, emulsions, sols, and gels, classified by dispersing medium and dispersed phase.

Colloids and solubility factors

Hydrophilic vs. hydrophobic tendencies and surface stabilization influence colloid stability in water.

Colligative properties

Properties that depend on the number of solute particles, not their identity; examples include vapor-pressure lowering, boiling-point elevation, freezing-point depression, and osmotic pressure.