I read that a buffer solution has its greatest buffer capacity when its pH = pKa. The pH part I get but how can a solution have a pKa? Ka is the dissociation constant of an acid. Does this mean that to get maximum buffer capacity, you should adjust the pH of the solution so it equals the pKa of the acid you use? Acetic acid has a pKa of around 4.8 so does this mean that if you use acetic acid and sodium acetate to make a buffer solution then you will have to lower the pH to 4.8 in order to get maximum buffer capacity?