HS is the Bronsted-Lowry base in the forward reaction.
The Brnsted-Lowry theory is an acid-base reaction theory that was independently proposed in 1923 by Johannes Nicolaus Brnsted and Thomas Martin Lowry.
An acid is a proton (H+) donor in the Brnsted-Lowry definition of acids and bases, and a base is a proton acceptor. A conjugate base is formed when a Brnsted-Lowry acid loses a proton. A conjugate acid is formed when a Brnsted-Lowry base gains a proton.
A Bronsted-Lowry base is a compound that accepts a proton or an H+ ion from another compound. A conjugated acid can donate a proton and reform the base. An acid-base reaction, according to the Bronsted-Lowry theory, involves the exchange of protons or H+ ions between the acid and base.
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