AP Chemistry Unit 3: Mechanics of Mixtures and Solubility

Mixture

A physical combination of two or more substances where the identity of each substance remains unchanged.

Heterogeneous Mixtures

Mixtures where components are not distinct and not uniformly distributed (e.g., salad dressing, concrete).

Homogeneous Mixtures

Mixtures where components are uniformly distributed at the microscopic level, often referred to as solutions.

Solution

A mixture composed of two distinct parts: solvent and solute.

Solvent

The substance present in the greatest abundance in a solution, typically water in aqueous solutions.

Solute

The substance being dissolved in a solution.

Molarity (M)

The standard unit of concentration in chemistry, defined as moles of solute per liters of solution.

Coulombic interactions

The stabilizing force between charged ions and polar water molecules.

Dissociation

The process when an ionic compound breaks apart into ions when dissolved in a solvent.

Solvatation

The process of surrounding solute particles with solvent molecules, also known as hydration when specifically involving water.

Miscible

Two liquids that mix in all proportions, such as ethanol and water.

Immiscible

Two liquids that form distinct layers and do not mix, such as oil and water.

Intermolecular Forces (IMFs)

Forces that determine the interaction between molecules, affecting solubility.

Golden Rule: 'Like Dissolves Like'

The principle that substances with similar intermolecular forces tend to be soluble in one another.

Retraction Factor (R_f)

A value that quantifies the distance traveled by a component in chromatography relative to the distance traveled by the solvent front.

Distillation

A process to separate components based on differences in boiling points and vapor pressures.

Chromatography

A technique to separate components based on differences in particle polarity and their affinity for stationary and mobile phases.

Mobile Phase

The solvent moving up the paper in chromatography, usually the eluent.

Stationary Phase

The paper or solid strip used in chromatography that does not move but interacts with the components being separated.

Ethanol

A polar solvent that can form hydrogen bonds with water, making it miscible with water.

Ionic Compound

A compound that dissociates into ions in a solvent, often soluble in polar solvents.

Cation

A positively charged ion that attracts the partially negative oxygen of water during solvatation.

Anion

A negatively charged ion that attracts the partially positive hydrogen of water during solvatation.

High R_f value

Indicates high attraction of a component to the mobile phase in chromatography, suggesting it is nonpolar.

Low R_f value

Indicates high attraction of a component to the stationary phase in chromatography, suggesting it is polar.

Total Volume of Solution

The volume used in calculating molarity, which includes both solute and solvent.

Dissociation vs. Decomposition

Dissociation refers to the breaking apart of an ionic compound into its constituent ions, while decomposition refers to breaking down a compound into smaller molecules or atoms.