Solution of a weak acid and its anion (that is,its conjugate base) or of a base and its common cation are buffered. When we add a small amount of acid or base to any one of the, the pH of solution change very little. pH of buffer solution can be computed as for acidic buffer : `pH=pK_(a)+ log.(["Conjugate base"])/(["Acid"])`
for basic buffer : `pOH=pK_(b)+log.(["Conjugate acid"])/([Base])`
It is generly accepted that a has useful buffer cpacity (pH change resisting power) provided that the value of [salt or conjugate base] /[acid] for acidic buffer lies within the range of 1 : 10 to 1. Buffer capacity is maximum when [conjugate base] = [acid]
Useful buffer range of weak acid `HA(K_(a)=10^(-5))` is :

Options

A. When we add small amount of NaOH in acidic buffer aolution, pHO of solution is increases
B. When we add small amount of NaOH in vasic buffer solution, pH of solution is increases
C. When we add small amount of water in acidic buffer solution , pH of solution is decreases
D. When 100 mL of 0.2 M `CH_(3)` COOH react with 200 mL of 0.1 M NaOH buffer solution is