Boric acid  $B{\left(OH\right)}_3$  is used as a mild antiseptic. What is the pH of a $0.0025M$ aqueous solution of boric acid? The hydrogen ion arises principally from the following reaction  $B{\left(OH\right)}_{3_{\left(aq\right)}}+H_2{O}_{\left(l\right)}\rightleftarrows B{\left(OH\right)}_4{{ }^{-}}_{{ }_{\left(aq\right)}}+{H^{\oplus }}_{{ }_{\left(aq\right)}},K=4.0\times {10}^{-10}$