\[
\begin{array}{|c|c|}
\hline \text{acid} & \text{chemical formula} \\
\hline \text{iodic acid} & \boxed{\text{HIO}_3} \\
\hline \text{sulfurous acid} & \boxed{\text{H}_2\text{SO}_3} \\
\hline \text{hydrosulfuric acid} & \boxed{\text{H}_2\text{S}} \\
\hline \text{nitrous acid} & \boxed{\text{HNO}_2} \\
\hline
\end{array}
\]