Question

What is the conjugate base of ${{H}_{2}}S{{O}_{3}}$?

Answer 1

A conjugate base is the product of a chemical process in which an acid donates a proton. As a result, a conjugate base is a species produced by removing a proton from an acid, as it may acquire a hydrogen ion in the opposite process. Because some acids may release numerous protons, the conjugate base of an acid can be acidic as well.

Complete answer:
Depending on which chemical is involved and which acid–base theory is used, a cation can be a conjugate acid and an anion can be a conjugate base. The solvated electron, whose conjugate acid is atomic hydrogen, is the simplest anion that may be a conjugate base.
In a nutshell, this may be expressed as the chemical reaction:
$Acid\text{ }+\text{ }Base\text{ }\rightleftharpoons \text{ }Conjugate\text{ }Base\text{ }+\text{ }Conjugate\text{ }Acid$
As you may be aware, an acid's conjugate base is identified by examining the molecule that remains after the acid transfers one of its acidic hydrogen atoms.
The base is the chemical to which the acid gives a proton. The acid's conjugate base will be the chemical that accepts a proton to reconstruct the acid.
Sulfuric acid has two protons to give in this scenario. However, when the first hydrogen ion is supplied, the conjugate base of sulphurous acid will be the chemical left behind.
${{H}_{2}}S{{O}_{3}}(aq)\rightleftharpoons {{H}^{+}}(aq)+HS{{O}_{3}}^{-}(aq)$
The bisulfate anion, $HS{{O}_{3}}^{-}$, is the chemical left over after sulfuric acid contributes its initial acidic hydrogen.
As you can see, the bisulphite anion may absorb a proton and rebuild the sulphurous acid.

Note:
Sulphur dioxide aqueous solutions, also known as sulphurous acid, as well as bisulfite and sulfite salt solutions, are employed as reducing agents and disinfectants. By absorbing another oxygen atom, they are oxidised to sulfuric acid or sulphate. Although no evidence of sulphurous acid in solution has been found, the molecule has been discovered in the gas phase.