How many acidic H + ion is given by H3BO3 in aqueous solution? ... ?

Boric acid, H3BO3, in aqueous solution would only give out one H + ion. As it is also produce OH ion and by hydrolysis it produces one proton. All the boron compounds (BX3) are having only 6 valence electrons in it and should follow the octet rule by taking another electron.

B (OH) 3 + 2 H2O → B (OH) 4 - + H3O