CHEM 132, Chapter 14

• Common ion effect


  A shift in equilibrium position that occurs because of an addition of an ion already involved in an equilibrium reaction
• Presence of a common ion

  Suppresses ionization of a weak acid or base
• Buffered solutions


  Resist change in pH with the addition of either acid or base
• pH buffer


  • Must contain weak acid or base, and the conjugate of the weak acid/base
  • Most effective when [HA]~[A-]
• Buffer capacity


  Dependent on the amount of acid and base
• Titration


  1. Determine the amount of acid or base in a solution

  2. Deliver titrant of known concentration from a buret into unknown solution until substance being analyzed is just consumed

  3. Equivalence point is where the amount of titrant has been added to exactly react with all analyze originally present

  4. Signaled by color change of the indicator
• Titration curve


  • A plot of pH of solution as titrant is added
  • The middle of the inflection is equivalence point
• Titration of strong acids with strong bases

  pH is 7
• Titration of weak acid and strong base

  Titration point is >7
• Titration of weak acid and weak base

  pH is <7