Buffers

[105747606]

For buffers, does the acid or base added to maintain the pH need to be weak, or can it be strong like HCl for example?

[Timothy Liu 3C]

I don't think you can have a buffer with a strong base or acid because those will ionize completely. If they ionize completely, then there will be nothing in the solution able to react with added acid or base to resist pH change.

[LenaNguyen]

Buffers are typically weak acids/bases as strong acids/bases would ionize completely, thus it cannot "buff" against pH changes due to added acids or bases.

From "Calculating the pH of a weak acid and its salt [ENDORSED]",

"Acidic buffers are made using a weak acid and adding its conjugate base as a salt so that the concentrations of weak acid (HA) and its conjugate base (A-) are approximately equal.

Basic buffers are made using a weak base and adding its conjugate acid as a salt so that the concentrations of weak base (B) and its conjugate acid (HB+) are approximately equal.

Having both the acid and base in approximately equal concentrations results in both being present to act as a buffer (neutralize an added base, or neutralize an added acid)."

[Brianna Bui 2J]

Hi,

buffers tend to be weak acids and bases because their disassociation has both forward and reverse reactions. In other words, they do not completely ionize/disassociate, so there are still reactants in the solution once the reaction has reached equilibrium. This means that the reverse reaction can proceed. Strong acids disassociate completely, so they cannot do the same, thus the best buffers cannot be strong acids/bases.