Why are buffers used?

[Chem_Mod]

Question: Why are buffers used? Isn't the addition of small amounts of acids or bases contradict the purpose of resisting a change of pH?

[Chem_Mod]

Answer: A buffer can resist pH change even with the addition of small amounts of strong acid or base (i.e. acids/bases that are not part of your buffer system). a buffer can effectively "absorb" added acid with little change in pH when [A-]/[HA] is at least 0.10. This is yet another way to say that the effective range for a buffer is pKa +/- 1. You can adjust the pH of your buffer system as desired by changing the ratio of [A-]/[HA] (i.e. the ratio of weak base to weak acid comprising your buffer system).