Buffer Solutions

Buffer Solutions

1. A buffer solution consists of a weak acid (to supply protons to any added OH-) and its conjugate weak base (to accept protons from any added H3O+), e.g. a mixture of ethanoic acid and sodium ethanoate

2. A buffer solution is a solution that resists changes in pH when small amounts of either acid or base are added

3. The pH of a buffer solution can be calculated by substituting the values for the concentrations of the weak acid and base into the Ka(acid) expression and solving for [H3O+]

   • HA + H2O <--> H3O+ + A-
   • Ka(acid) = [H3O+]*[weak base]/ [weak acid]
     • Or the logarithmic form: pH = pKa + log[weak base]/[weak acid]

4. In general, in a buffer solution, [H3O+] does NOT equal {A-]