Hydrogen sulfide (HS–) is a weak base. It can accept a proton (H+) to form its conjugate acid, which is H2S (hydrogen sulfide). This can be understood through the Brønsted-Lowry acid-base theory, where an acid is a substance that donates protons and a base is one that accepts protons.
When HS– accepts a proton, the reaction can be represented as:
HS– + H+ → H2S
Therefore, the conjugate acid of HS– is H2S.
Conversely, H2S can donate a proton to form its conjugate base, HS–.