what is the pH of a 0.100 M solution of HA if 7% of the acid is dissociated?
..............HA ==> H^+ + A^-
initial.......0.100...0.....0
change.......-0.007...0.007..0.007
7% ionization means that 0.07 x 0.1M is the (H^+).
Then pH = -log(H^+).