Final answer:
The conjugate base of HSO₃⁻ is SO₃²⁻, which is formed when HSO₃⁻ donates a proton.
Step-by-step explanation:
The conjugate base of HSO₃⁻ is obtained by the removal of a proton (H+). The sulfite ion (SO₃²⁻) is what remains after HSO₃⁻ donates a proton and therefore, is its conjugate base. Therefore, the correct answer is 4) SO₃²⁻. To clarify, when HSO₃⁻ loses a hydrogen ion (H+), it forms SO₃²⁻, which can then act as a base and accept a proton in a reverse reaction, making it the conjugate base.
The process can be represented as follows:
HSO₃⁻(aq) → H+(aq) + SO₃²⁻(aq)