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Chapter 17: Solutions and Solubility

Overview

• Focus on various sections including definitions, intermolecular forces, solubility, and colligative properties.

• Discuss the significance of solute and solvent components and their interactions.

Definitions

• Solutions: Homogeneous mixtures composed of two main components.

  • Solute: The substance that dissolves.

  • Solvent: The substance present in the larger amount.

    • Example: In a solution of saltwater, water is the solvent, and salt is the solute.

Types of Mixtures

• Matter Classification: Divided into two main categories:

  • Pure Substances: Elements and compounds.

  • Mixtures: Further classified into homogeneous and heterogeneous mixtures.

    • Solutions are a type of homogeneous mixture.

Solution Formation

• Process: When an ionic crystal (e.g., sodium chloride) is added to water:

  1. Ionic structure remains initially intact.

  2. Water molecules interact with individual ions.

  3. Ions are surrounded by water molecules and dispersed throughout the solution.

  • Completion of this process means solute is dissolved in the solvent.

Intermolecular Forces

• Competing Forces in solution formation:

  • Solvent-solvent forces

  • Solute-solute forces

  • Solute-solvent forces

• For effective dissolution:

  • Solvent-solvent and solute-solute forces must be comparable to solute-solvent forces.

  • Golden Rule: "Like dissolves like" - similar types of solutes and solvents are likely to mix.

Types of Solutions

• Classification: Different types based on physical states:

  • Solid-Liquid: Common types like saltwater.

  • Solid-Solid: Alloys like gold (14 carat = 58% gold).

  • Gas-Gas: Air (mainly nitrogen 78% and oxygen 21%).

Terms in Solutions

• Miscible vs. Immiscible:

  • Miscible: Two liquids that can dissolve completely (e.g., ethanol in water).

  • Immiscible: Liquids that do not mix (e.g., oil and vinegar).

  • Partially Miscible: Slight solubility (e.g., dimethyl ether in water due to differences in strength of intermolecular forces).

Solubility Limitations

• Factors influencing solubility:

  • Maximum amount of solute depends on temperature and pressure for gaseous solutions.

  • Solids and liquids are typically unaffected by pressure.

• Equilibrium: At saturation, the rates of dissolving and crystallization equalize, leading to three types of solutions:

  1. Saturated: Maximum solute dissolved; any excess does not dissolve.

  2. Unsaturated: Less solute than the maximum can still dissolve.

  3. Supersaturated: More solute than the maximum; achieved when heated and then cooled, but unstable and sensitive to disturbances.