\(\mathrm{E}=\mathrm{E}^0-\frac{0.059}{\mathrm{n}} \log \frac{\mathrm{P}_{\mathrm{H}_2}}{\left[\mathrm{H}^{+}\right]^2}\)
\(0=0-\frac{0.059}{2} \log \frac{\mathrm{P}_{\mathrm{H}_2}}{\left(10^{-7}\right)^2}\)
\(\log \frac{\mathrm{P}_{\mathrm{H}_2}}{\left(10^{-7}\right)^2}=0\)
\(\frac{\mathrm{P}_{\mathrm{H}_2}}{10^{-14}}=1\)
\(\mathrm{P}_{\mathrm{H}_2}=10^{-14} \text { bar }\)
$H_3PO_4 + OH^- \rightarrow H_2PO_4^- + H_2O$ ;
$H_3PO_4 + 2OH^- \rightarrow HPO_4^{2-} + 2H_2O$ ;
$H_3PO_4 + 3OH^- \rightarrow PO_4^{3-} + 3H_2O$