# Why is buffer capacity at a maximum when the ratio of its components is 1? [duplicate]

A buffer consists of a weak acid and its salt or weak base and its salt.

When the ratio of weak acid and its salt in a buffer (or the ration of weak base and its salt) is equal to 1, we say that the buffer capacity is maximum. How does this tell us that buffer capacity is maximum?

$$\mathrm{pH} = \mathrm{pK}_{a} + \log\frac{\ce{[A-]}}{\ce{[HA]}}$$
Now, your ability to neutralize acid is determined by the amount of the conjugate base $\ce{A-}$. Your ability to neutralize base is determined by the amount of the acid $\ce{HA}$. When the ratio between these is 1, you have equal ability to neutralize either. If you're skewed too far one way or the other, then you will not have much of the respective species around to neutralize added acid or base.
• Shouldn't the ability to neutralize base is determined by by amount of $H^+$.Why have you written "ability to neutralize base is determined by the amount of the acid $HA$"? – pranjal verma Jan 20 '19 at 11:08