The Effectiveness of a Buffer
Suppose we drop 0.01 moles of strong base into our buffer from the last example. What will be the measured effects?
 
            HA     +   OH- <------->  A-       +    H2O
start   0.09 M      -----               0.11 M
finish -0.01 M    -0.1 M           +0.01 M
          0.08 M      0.0 M            0.12 M
 
pH = pKa + log [anion]
                          [acid]

      = 4.74 + log (0.12)
                          (0.08)
 

      = 4.74 + log 1.5
      = 4.74 + 0.18
      = 4.92     The change in pH is small compared to what it would have been in pure water!