Well what does pKa mean? Remember that the the pKa is the -log (p function) of the ionization constant of that particular acid. So if you were going to design a buffer for a particular acid then the pH of the buffer would need to be within +/- 1 unit of the pKa of the acid. Also remember that the pH is the -log of the [H30+]. So if the pKa were within +/-1 pH unit of the buffer than the buffer would provide its greatest buffering capacity to the solution by offering a relatively equal amount of base to neutralize any acid that dissociates. Recall that the concentration of the base is roughly equal to the concentration of the acid in the buffered solution within the +/-1 range.
Ex: If you had an acetic acid/sodium acetate solution at a pH = 3.6. Then this solution would effectively have the greatest buffering capacity for all acids with a range of pKa's between 2.6 and 4.6.
Don't let my GC score on predents fool you either...i didnt study for the DAT.
