Answer
Hydrogen carbonate** ($HC{O_3}^-$) is the conjugate partner of $H_2CO_3$
The most common name is bicarbonate.
Work Step by Step
1. Identify if the substance is an acid or a base (or both):
- $H_2CO_3$ is an acid.
2. Since $H_2CO_3$ is an acid, remove one proton from it:
- Remove one hydrogen and subtract one from the charge:
$H_2CO_3 -- \gt HC{O_3}^-$
- This is the conjugate base of $H_2CO_3$.
3. Name it:
$C{O_3}^{2-}$: Carbonate ion.
$HC{O_3}^- = H^+ + C{O_3}^{2-}$; Therefore:
$HC{O_3}^-$: Hydrogen carbonate.
** The most common name for it is "bicarbonate", but the IUPAC recommended is "hydrogen carbonate".