Chemistry Module 5: Equilibrium and Acid Reactions

EQUILIBRIUM AND ACID REACTIONS NOTES

STATIC AND DYNAMIC EQUILIBRIUM

  • Inquiry question: What happens when chemical reactions do not go through to completion?
  • Investigate reversibility of reactions:
    • Cobalt(II) chloride hydrated/dehydrated
    • Iron(III) nitrate and potassium thiocyanate
    • Burning magnesium and steel wool
  • Model differences between static and dynamic equilibrium:
    • Open vs. closed systems
    • Examples: combustion reactions, photosynthesis
  • Analyze collision theory and reaction rate relationships with chemical equilibrium.

FACTORS AFFECTING EQUILIBRIUM

  • Inquiry question: What factors affect equilibrium and how?
  • Investigate effects of temperature, concentration, pressure, and volume:
    • Heating cobalt(II) chloride hydrate
    • Interaction between nitrogen dioxide and dinitrogen tetroxide
    • Iron(III) thiocyanate with varying ion concentration
  • Explain equilibrium observations via collision theory.
  • Examine activation energy and heat of reaction impacts on equilibrium position.

CALCULATING THE EQUILIBRIUM CONSTANT (Keq)

  • Inquiry question: How can the position of equilibrium be described?
  • Deduce equilibrium expression (Keq) for homogeneous solution reactions.
  • Perform calculations for Keq & concentrations to predict reaction direction.
  • Qualitatively analyze Keq's temperature dependence.
  • Examples include ionic solution dissociation and acids/bases.

SOLUTION EQUILIBRIA

  • Inquiry question: How does solubility relate to chemical equilibrium?
  • Describe processes for dissolving ionic compounds in water.
  • Investigate solubility equilibria in Aboriginal and Torres Strait Islander practices, like toxin removal.
  • Conduct experiments for solubility rules, predicting compositions from mixed ionic solutions.
  • Derive equilibrium expressions for saturated solutions with Ksp; calculate solubility.

REVERSIBLE REACTIONS

  • Equilibrium types: Static (irreversible) vs. Dynamic (reversible).
  • Impact of closed systems on equilibrium; a dynamic state exists even at equilibrium.
  • Factors affecting equilibrium include:
    • Concentration/Volume/Pressure
    • Temperature
    • Collision theory (effective collisions required for reactions)

GIBBS FREE ENERGY & SPONTANEITY

  • Gibbs energy (ΔG) indicates spontaneity:
    • ΔG < 0: spontaneous reaction
    • ΔG > 0: non-spontaneous
    • ΔG = 0: reaction is at equilibrium.

ACID-BASE REACTIONS AND KINETICS

  • Strong vs. Weak Acids:
    • Strong acids: complete dissociation (e.g., HCl, H2SO4)
    • Weak acids: partial dissociation (e.g., acetic acid)
  • Indicators for acid-base titrations and their pH impact at equivalence points.
  • Primary vs secondary standards in quantifying concentrations.

BUFFER SOLUTIONS

  • Buffers resist pH changes due to added acids/bases.
  • Typically made from weak acids and their conjugate bases.
  • Buffer capacity can be defined by the resistance to pH change and requires similar concentrations of acid and base.

TITRATION PROCEDURES

  • Stepwise for analysis includes balanced equations, mole calculations, and proper volumes.
  • Use Burette for precise titrant delivery; observe endpoint shifts closely.
  • Analyze buffers, acid/base nature in the context of real-world applications, including cultural practices in food safety.

FINAL REMINDERS

  • Definitions of acids/bases (Arrhenius, Bronsted-Lowry)
  • pH scale understanding (7 neutral; implication on acidity/basicity)
  • Calculate pH, [H+], and [OH-] well, keeping logarithmic scaling in mind.

SOLUBILITY PRODUCT CONSTANT (Ksp)

  • Understanding Ksp allows predicting precipitation from ionic combinations.