Acids, bases & pH

• Why is H20 not shown in kW expression?

  H20 has almost constant value. H20 very large in comparison to H+ & OH-. Equilibrium lies to the left.
• What are acids?


  Proton donors
• What are bases?

  Proton acceptors
• HA + H2O...


  H3O+ + A-
• B + H20...


  BH+ + OH-
• HA + B...


  BH+ + A-
• Monoprotic


  acid released 1 proton when it dissociates
• What is a buffer?


  Solution that resists changes in pH when small amounts of acid or alkali are added.
• What is an acidic buffer?


  pH less than 7- contain mixture of weak acid with one of its salts.
• What are basic buffers?

  Ph over 7- contain mix of weak base with 1 of its salts.
• How can buffers resist pH changes when diluted by water?

  Water slightly dissociates- extra H+ & OH- push equilibrium same amount in both directions.
• Why are buffers added to shampoo?

  Alkaline conditions make surface of individual hairs rougher, so most shampoos have pH 5.5 to keep hair smooth & shiny.
• Why do biological washing powders contain buffers?

  Keep pH at right level for enzymes to work best.