1. Chapter 9
More on buffers

2. Buffers
A buffer is a solution whose pH changes very little when acid or base is added
Most buffers are solutions composed of roughly equal amounts of:
A weak acid
The salt of its conjugate base
A salt is usually a positive metal ion bound to a negative non-metal ion
The buffer resists change in pH because
Added base, OH−, reacts with the weak acid
Added acid, H3O+, reacts with the conjugate base

3. Buffer example: HF
Most buffers are solutions composed of roughly equal amounts of:
A weak acid: example HF
Some will dissociate to H3O+ and F- which will result in an acidic pH
The salt of its conjugate base: example F- from NaF
Na+ will also be in solution but it is a spectator ion that does not contribute to pH F-
When acid (H3O+) is added:
H3O+ + F-  HF + H2O
H3O+ + F- interact to make HF and water, so there is only a slight change in pH F- HF F- HF HF F- HF F- HF F- HF F- HF F- F- F- F- HF HF
When base (OH-) is added:
OH- + HF  F- + H2O
OH- + HF interact to make F- and water, so there is only a slight change in pH F- HF F- HF HF F- HF HF

4. Buffers - generalized
Most buffers are solutions composed of roughly equal amounts of:
A weak acid, HA
The salt of its conjugate base, A- A-
When H3O+ is added it interacts with the conjugate base to form more of the weak acid A- HA A- HA HA A- HA A- HA A- HA A- HA A- A-
When OH- is added it interacts with the weak acid to form water and more of the conjugate base A- A- HA HA A- HA A- HA HA A- HA HA