The conjugate base of HS⁻ (hydrogen sulfide ion) is S²⁻ (sulfide ion).
When HS⁻ loses a proton (H⁺), it forms S²⁻. This process is represented by the following chemical equation:
HS⁻ → S²⁻ + H⁺
In this reaction, HS⁻ acts as an acid by donating a proton, and S²⁻ is its conjugate base. The concept of conjugate acids and bases is fundamental in understanding acid-base reactions and the behavior of substances in different chemical environments.