solutions

Matter

• Matter: Can exist in different forms and can be classified.

  • Can it be physically separated?

    • Yes:

      • Homogeneous Mixture (solution)

      • Heterogeneous Mixture

    • No:

      • Compound

      • Element

  • Mixture vs. Pure Substance

    • Mixtures are variable combinations of substances.

    • Pure substances have uniform composition.

Mixtures

• Types of Mixtures:

  • Homogeneous Mixtures:

    • Even distribution of components (Solutions)

  • Heterogeneous Mixtures:

    • Uneven distribution of components.

    • Includes Suspensions and Colloids.

Homogeneous Mixtures

• Examples:

  • Alloys: Solids dissolved in other solids.

    • Example: 10 K gold = gold + copper; brass = copper + zinc.

  • Air: Oxygen and other gases dissolved in nitrogen.

  • Solutions: Very small particles that do not settle.

    • Example: Salt water, rubbing alcohol.

Heterogeneous Mixtures

• Colloids:

  • Medium-sized particles that do not settle.

    • Example: Milk, jello, fog.

• Suspensions:

  • Large visible particles that do settle when at rest.

    • Example: Lemonade, orange juice.

Solutions

• Definition:

  • Homogeneous mixtures where one substance is dissolved in another.

  • Particles are too small to be seen and do not settle.

• Parts of a Solution:

  • Solute: Component being dissolved (e.g., salt in salt water).

  • Solvent: Component doing the dissolving (e.g., water in salt water).

  • Aqueous: Water as the solvent.

  • Tincture: Alcohol as the solvent.

Solvation

• Definition: Process of dissolving, involving several steps:

  • Solute particles separate from the surface of the solid solute.

  • Solvent molecules move apart for solute molecules to enter.

  • Solute molecules are attracted to solvent molecules until completely dissolved.

Aqueous Solutions

• Definition: Water as the solvent in solutions.

  • Examples: Seawater, rain, cola, wine, vinegar.

Ionic Compounds in Aqueous Solution

• Dissociation: Separation of ionic solids into aqueous ions (e.g., NaCl dissociates into Na+ and Cl- in water).

Molecular Compound Solvation

• Dispersion: Molecules stay intact and do not separate (e.g., C6H12O6 remains C6H12O6(aq)).

Solubility Concept

• Definition: Measure of how much solute can be dissolved in solvent under specified conditions.

• Factors Affecting Solubility:

  • Nature of solute and solvent.

  • Temperature.

  • Pressure.

  • Surface area.

  • Agitation.

Solubility Rules

• Salts containing Group I elements are usually soluble with rare exceptions.

• Salts containing nitrate ion (NO3-) are generally soluble.

• Exception cases: Halides such as AgCl, PbBr2, and Hg2Cl2 are insoluble.

Factors Affecting Rate of Solubility

• Key Factors:

  • Size of solute crystals (surface area).

  • Vigorous and duration of stirring.

  • Temperature of the solvent (higher temperature for solids increases solubility, but for gases, it declines).

  • Pressure affects solubility of gases significantly.

Rate of Solubility Enhancements

• Methods:

  • Stirring: Increases molecular collisions.

  • Powdering solid solute: Increases surface area.

  • Heating solution: Increases particle motion.

Electrolytes vs. Nonelectrolytes

• Electrolytes: Substances that dissociate into ions in solution and conduct electricity.

  • Examples: HCl, MgCl2, NaCl.

• Nonelectrolytes: Substances that dissolve but do not conduct electricity (e.g., sugar, ethanol).

Conductivity Summary

• Essential Points:

  • Ions must be present to conduct electricity.

  • Dissociation is the separation of ions in solution.

  • Electrolytes: Conductors due to ionization.

  • Nonelectrolytes: No charged particles in the solution.

Types of Solutions

• Liquid Solutions:

  • Miscible: Two liquids that dissolve in each other.

  • Immiscible: Two liquids that do not dissolve in one another (e.g., oil and water).

• Solid Solutions:

  • Alloys: Mixtures of two or more metals.

Concentration of Solutions

• Definitions:

  • Concentrated: High solute amount relative to solvent.

  • Diluted: Low solute amount relative to solvent.

  • Saturated: No more solute can dissolve.

  • Unsaturated: Can still dissolve more solute.

  • Supersaturated: Contains more solute than can normally be dissolved.

Molarity Concepts

• Definition: Molarity (M) = moles of solute / liters of solution.

• Connection between molarity and concentration.

• Dilution Formula: M1 * V1 = M2 * V2 (Molarity and Volume relation before and after dilution).