According to the Henderson–Hasselbatch equation when pH = Pka for any buffer solution then why we say that this is the best buffer?
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1$\begingroup$ Related: Why is Buffer capacity maximum when the ratio of its components is 1? $\endgroup$ – Loong♦ Mar 27 '16 at 11:48
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When we say it's the best buffer, we mean that the solution can resist pH change in either direction, and this occurs when $\ce{pH=pK_a}$. In the Henderson-Hasselbatch equation, $\ce{pH = pK_a + log\frac{[base]}{[acid]}}$, this is achieved as long as [base] = [acid]. The actual amounts of the acid and base forms, however, determines how far it can resist pH change.
