Module 4

• Acid


  A species which donates protons in a reaction (Lowry-Bronsted) or accepts electrons (Lewis)
• Base


  A species which accepts protons in a reaction (Lowry-Brensted) or donates electrons (Lewis)
• Complex


  A compound formed in a complexation reaction between two or more species which are capable of independent existence
• Ligand


  A species with at least one Lewis basic site which can participate in complex formation
• Strong Electrolyte


  A compound which is almost completely dissociated in solution
• Weak Electrolyte


  A compound which remains significantly undissociated in solution
• 'p' Notation


  Used for convenience in handling quantities which vary in magnitude through many powers of ten
• Le Châtelier's principle


  States that the position of an equilibrium always shifts in such a direction as to relieve a stress that is applied to the system
• Mass-action effect


  A shift in the position of an equilibrium caused by adding one of the reactants or products to a system
• Henderson-Hasselbalch equation


  Used to calculate the pH of buffer solutions in the form of its negative logarithm and inverting the concentration ratio to keep all signs positive
• Ka, pKa, Kb, and pKb


  Most helpful when predicting whether a species will donate or accept protons at a specific pH value; describe the degree of ionization of an acid or base and are true indicators of acid or base strength
• Ka


  The acid dissociation constant
• pKa


  Is simply the -log of the acid dissociation constant
• Kb


  The base dissociation constant
• pKb


  The -log of the base dissociation constant
• Aqueous


  Solution in which the solvent is water
• Electrolytes


  Substances that have a natural positive or negative electrical charge when dissolved in water
• Strong electrolytes


  Ionize essentially completely in a solvent
• Weak electrolytes


  Ionize only partially
• Conjugate base


  Is formed when an acid loses a proton
• Conjugate acid


  Is formed when a base accepts a proton
• Strong acid


  Any acid that dissociates 100% into ions
• Weak acid


  Does not dissociate 100% into ions
• Strong base


  A base that is 100% ionized in solution
• Weak base


  Less than 100% ionized in solution
• Equilibrium Constants


  Defined as the ratio between the amount of reactant and the amount of product which is used to determine chemical behaviour
• Solvent Effects


  The influence of a solvent on chemical reactivity or molecular associations
• Temperature Effects on Equilibrium Constants

  1. If heat is applied to an endothermic reaction K_e will increase

  2. Heat applied to an exothermic reaction will result in a decrease in K_e

  3. Heat will tend to increase the disorder of the system and favor the side of the reactant with the greatest potential disorder
• Increasing the temperature decreases the value of equilibrium constant
• Ionizing Solvent


  Polar or ionic in nature; weak conductor of electricity
• Ionizing Solvent


  • Bromine
  • Trifluoride
  • Phosphorus
  • Oxychloride
• Non-ionizing Solvent


  Dissolved only non-polar compound
• Non-ionizing Solvent


  • Benzene
  • Carbon tetrachloride
• Buffer


  A solution that contains a constant pH when an external acid and a base is added unto it
• Complexation Equilibria


  When a metal ion reacts with a Lewis base in solution a complex ion is formed
• Solubility Equilibria


  A solubility equilibrium exists when a chemical compound in the solid state is in chemical equilibrium with a solution containing the compound
• Three main types of solubility equilibria

  • Simple dissolution
  • Dissolution with dissociation reaction
  • Dissolution with ionization reaction
• Dissolution with dissociation reaction

  Characteristic of salts; the equilibrium constant is known in this case as a solubility product
• Dissolution with ionization reaction


  Characteristic of the dissolution of weak acids or weak bases in aqueous media of varying pH