A Bronsted-Lowry acid is a proton ( H+ion) donor while Bronsted-Lowry base is a proton (H+ ion) acceptor. HSO4−+H2O⇌H2SO4+OH− (Bronsted based) HSO4−+H2O⇌SO42−+H3O+ (Bronsted acid) HSO4−act as a conjugate base of sulphuric acid and does not give H+.SO42− is a conjugate base of HSO4− and does not get ionised further. Thus, HSO4−is Bronsted acid as well as Bronsted base.