Buffers

Living things can only tolerate a narrow range of pH. Coral reefs for example grow best at pH of 8.2 - 8.5. Our blood is maintained between pH of 7.35 - 7.45. Buffer solutions provide living things with the mechanism they need to control the range of pH.

So far we discussed that acids and bases break into ions in water. 

ex. HCl(s)+ H2O(ℓ) →  H+(aq) + Cl−(aq) [~100%]

But this process is not always complete. Only strong acids or strong bases complete dissociate in water. For example acetic acid (found in vinegar) only dissociates about 1%

ex. CH3COOH(aq)+ H2O(ℓ) ⇌  H+(aq) + CH3COO−(aq) [~1%]

The dissociation constant for acids (Ka) is basically the equilibrium constant for the reaction. 

Weak acids and bases will have K constants below zero while strong acids and bases will have K constants well above zero. 

Buffer solutions have a limited capacity to resist pH change. Meaning that they do not change pH much when acid or base is added. 

Buffers are created by mixing a solution of a weak acid and one of its salts or a weak base and one of its salts. 

Buffers do this because they have one component that can react with H+ ions (an H+ ion acceptor) and another component that can react with the OH− ions (an H+ ion donor).

Buffer capacity

Buffers act like sponges that absorb acid or base, but they have a limited capacity. This depends on the amount of acid/salt or base/salt present in the system.