The pH of basic buffer mixtures is given by : `pH=pK_(a)+log((["Base"])/(["Salt"]))` , whereas pH of acidic buffer mixtures is given by: `pH= pK_(a)+log((["Salt"])/(["Acid"]))`. Addition of little acid or base although shows no appreciable change for all practical purpose, but since the ratio `(["Base"])/(["Salt"])` or `(["Salt"])/(["Acid"])` change, a slight decrease or increase in pH results in.
A weak acid HA after treatment with `12 mL of 0.1M` strong base BOH has a `pH=5`. At end point, the volume of same base required is `26.6mL K_(a)` of acid is: