Chemistry Notes - Acid-Base Theory, Intermolecular Forces, Solutions

Acid-Base Theory

  • Conjugate Acids and Bases
    • Strong acids have weak conjugate bases.
    • More stable conjugate bases are less reactive.
    • Example:
    • $HCl \rightarrow Cl^-$

Types of Acid-Base Reactions

  • Brønsted-Lowry Theory

    • Definition: An acid is a proton donor, while a base is a proton acceptor.

  • Lewis Theory

    • Definition: An acid is an electron pair acceptor, while a base is an electron pair donor.

Intermolecular Forces

  1. Dispersion Forces

    • Result from momentary induced dipoles between molecules.
    • Weakest of all intermolecular forces.

  2. Dipole-Dipole Interactions

    • Occur in polar covalent compounds; stronger than dispersion forces.
    • Higher boiling points due to stronger permanent charges.

  3. Hydrogen Bonding

    • Special case of dipole-dipole involving hydrogen and a small electronegative atom (like O, N, or F).
    • Significantly enhances boiling points of compounds.

Solutions

  • Miscible Liquids:

    • Definition: Homogeneous mixtures of two or more substances.
    • Example: Sugar dissolved in water.

  • Immiscible Liquids:

    • Definition: Do not mix, forming separate layers (e.g., oil and water).

  • Solubility

    • Maximale concentration achievable under specified conditions at equilibrium.
    • Saturated Solution: Concentration equals solubility.
    • Unsaturated Solution: Concentration less than solubility.
    • Supersaturated Solution: Concentration higher than solubility.

Electrolytes

  • Strong Electrolytes:

    • Completely ionize in solution (e.g., NaCl).

  • Weak Electrolytes:

    • Partially ionize in solution (e.g., $HCl_{2}O$) and conduct electricity poorly.

Colligative Properties

  • Vapor Pressure Lowering

    • Non-volatile solutes decrease vapor pressure of solvent.
    • Raoult´s Law: Partial pressure of a component is the product of its mole fraction and vapor pressure in pure state.

  • Boiling Point Elevation

    • Caused by the addition of a solute, lowering vapor pressure; requires higher temperature for vaporization.
    • $ riangle Tb = kb \cdot m$ where $m$ = molality, $k_b$ = ebullioscopic constant.

  • Freezing Point Depression

    • Solutions freeze at lower temperatures compared to the pure solvent.
    • $ riangle Tf = kf \cdot m$ where $m$ = molality, $k_f$ = cryoscopic constant.

Henry's Law

  • States solubility of a gas is directly proportional to its partial pressure above the liquid.
  • Formula: $Cg = kH \cdot Pg$ where $Cg$ = concentration of gas,
    $kH$ = Henry's law constant, $Pg$ = partial pressure of the gas.

Chemical Reactions

  • Reversible Reactions:
    • Can proceed in both forward and reverse directions.
    • Equilibrium exists when rates of forward and reverse reactions are equal.
    • Concentrations remain constant over time but are not necessarily equal.

Examples and Applications

  • The concepts above are fundamental to understanding acid-base reactions, solubility, solutions, and practical applications in equilibria. To solve specific problems or calculations, ensure to correctly apply the relevant equations such as those for colligative properties, Raoult's Law, and Henry's Law.