Why can hso4 - be both a base and an acid?

Answer 1

HSO4 can act as a base by gaining a hydrogen ion to make H2SO4. HSO4 can act as an acid by losing a hydrogen ion to make SO4.

Answer 2

HSO4- can act as both a base and an acid because it can accept a proton (H+) to form H2SO4 in an acidic solution (acting as a base) or donate a proton to form SO4^2- in a basic solution (acting as an acid). This dual behavior is due to the presence of a hydrogen ion that can be transferred depending on the conditions.