equilibrium in acid-base reactions

Question 1

what is the equilibrium expression for the dissociation of a weak acid, ha?

Answer 1

ka = [h+][a-][ha], where ka is the acid dissociation constant.

Question 2

how is the ph of a solution related to the concentration of hydrogen ions at equilibrium?

Answer 2

ph is the negative logarithm of the hydrogen ion concentration: ph = -log [h+].