[red_ryder]

Hi all. Appreciate if you could help on this very basic question.

I read in a textbook that if pH = pKa, then the compound is 50% dissociated.

Lets say the compound HA is dissociating to H+ and A-. If pH = pKa, I can do the math and get [HA] = [A-]. What I don't get is how that translates to 50% dissociation?

I thought 50% dissociation would be [A-] = 0.5 [HA]?

[FreeTheBee]

What happens to [HA] when it starts to dissociate to [H+] and [A-]?