4.27

\begin{array}{l|l}
Aine\ 1&Aine\ 2\\
\hline
HCOOH&HCOO^-\\
HPO_4^{2-}&H_2PO_4^-\\
NH_4^+&NH_3\\
\left(CH_3\right)_2NH&\left(CH_3\right)_2NH_2^+\\
CH_3CH_2COO^-&CH_3CH_2COOH
\end{array}