Answer
\begin{matrix}
Acid & Conjugate \space Base \\
HI & I^-\\
HCl & Cl^-\\
N{H_4}^+ & NH_3\\
H_2S & HS^-
\end{matrix}
Work Step by Step
1. To find the conjugate base of an acid, just remove one proton $(H^+)$ from it.
- Remove a hydrogen, and subtract one from the charge.
$HI \longrightarrow I^-$
$N{H_4}^+ \longrightarrow NH_3$
2. To find the conjugate acid of a base, just add one proton $(H^+)$ to it.
- Add a hydrogen, and sum one to the charge.
$Cl^- \longrightarrow HCl$
$HS^- \longrightarrow H_2S$
