01How much it can absorb
Buffer capacity is how much acid or base a buffer can neutralize before pH changes sharply. Higher concentrations of HA and A⁻ = higher capacity.
Best capacity when [HA] ≈ [A⁻] (pH ≈ pKa). A buffer works within about pKa ± 1.
02Notebook box
Capacity ∝ amount; pH ∝ ratio.
Worked example: 1.0 M/1.0 M vs 0.1 M/0.1 M buffer — same pH, the 1.0 M one resists 10× more acid.