Although it doesn't particularly want to give up a proton itself, boric acid, B(OH)3, acts as an acid in water because of the reaction:
B(OH)3 + H20 <-> B(OH)4^-1 + H+
Given that the Ka of boric acid is 5.8x10^-10M, what is the pH of a 0.50M boric acid solution? Are there any good approximation available?