In the reaction between hydrogen sulphate ion and water HSO4 + H20 H30+ + SOj- the water acts as

In the reaction HSO4- + H2O → H3O+ + SO4^2-, the behavior of the reactants is defined by the Brønsted-Lowry theory. According to this theory, an acid is a proton (H+) donor, while a base is a proton acceptor. In this specific chemical equation, the hydrogen sulphate ion (HSO4-) donates a proton to the water molecule, thereby acting as the acid. Conversely, the water molecule (H2O) accepts this proton to form the hydronium ion (H3O+), which identifies water as a base in this context. This reaction demonstrates the amphoteric nature of water, as it can act as either an acid or a base depending on the reactant it is paired with. Here, because water accepts a proton to become its conjugate acid (H3O+), it strictly functions as a Brønsted-Lowry base.