AP Chemistry Unit 8.8 Properties of Buffers

What is a Buffer?

  • A weak acid and its conjugate base is present in some form (usually within a salt)
  • A weak base and its conjugate acid is present in form form (usually within a salt)
  • A buffered solution/purpose of a buffer resists changes in pH when either H+ or OH- are added

Adding a Strong Acid  

  • Adding a strong acid to a weak acid buffer system → the strong acid will add its proton to the conjugate base
    • List out major species
      • Notes: water will always be a major species; strong acid will break up into its ions; a weak acid will remain whole)
    • Consider candidates for acids → Pick the strongest acid
      • Always choose H+ ion if present
    • Consider candidates for bases → Pick the strongest base
      • Always choose OH- ion if present
      • Do not pick a base that forms a strong acid

Adding a Strong Base

  • Adding a strong base to a weak acid buffer system → the strong base will take proton from the weak acid
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