I would like to type a list of chemical reactions with their associated reaction constants, pH limits and redox potentials. The reaction would be on the left, with the reaction starting at the left edge of the page, and the reaction constant would one line below, right-aligned to the rightmost part of the page. I tried a bunch of things with align, flalign, multline, ... but there always seem to be an issue. Here are my two best tries:
\documentclass{article}
\usepackage{amsmath,amssymb}
\usepackage[separate-uncertainty=true, locale=US, range-phrase={\,-\,}]{siunitx}
\usepackage[version=4, arrows=pgf]{mhchem}
\usepackage{chemmacros}
\begin{document}
\verb+flalign+ with \verb+aligned+ in it:
\begin{flalign}
&\ce{Cu2(OH)3Cl(s) <=> 2Cu^{2+} + Cl- + 3HO-} && \\
&&&
\begin{aligned}
K_a &= \frac{h^3}{[\ce{Cu^{2+}}]^2[\ce{Cl-}]} \\
\pH &= \frac{1}{3} (pK_a - 2 \log[\ce{Cu^{2+}}] - \log[\ce{Cl-}]) \\
&= \frac{1}{3} (\num{8.35} - 3 \log c_{\text{tra}} )
\end{aligned} \nonumber
\\
& \ce{Cu2(OH)3Cl(s) + 2e- <=> Cu2O(s) + HO- + H2O + Cl-} && \\
&&&
\begin{aligned}
E &= E°(\ce{Cu^{2+}}/\ce{Cu+}) + \num{0.06}\log\left(\frac{[\ce{Cu^{2+}}]}{[\ce{Cu+}]}\right) \\
&= E°(\ce{Cu^{2+}}/\ce{Cu+}) + \num{0.06}\log\left(\sqrt{\frac{h^3}{K_a [\ce{Cl-}]}} \frac{[\ce{HO-}]}{\sqrt{K_{s1}}}\right) \\
&= E°(\ce{Cu^{2+}}/\ce{Cu+}) + \num{0.06} \frac{1}{2} \log h
+ \num{0.06} \left(\frac{1}{2} \log \frac{K_e^2}{K_a K_{s1}} - \frac{1}{2}\log[\ce{Cl-}] \right) \\
&= \SI{0.47}{V} - \num{0.03}\log c_{\text{tra}} - \num{0.03} \pH
\end{aligned} \nonumber
\end{flalign}
\verb+subequations+ with \verb+flalign+ in it:
\begin{subequations}
\begin{flalign}
& \ce{Cu2(OH)3Cl(s) + 2e- <=> Cu2O(s) + HO- + H2O + Cl-} &
\end{flalign}
\begin{flalign*}
&& E = E°(\ce{Cu^{2+}}/\ce{Cu+}) + \num{0.06}\log\left(\frac{[\ce{Cu^{2+}}]}{[\ce{Cu+}]}\right) \\
&& = E°(\ce{Cu^{2+}}/\ce{Cu+}) + \num{0.06}\log\left(\sqrt{\frac{h^3}{K_a [\ce{Cl-}]}} \frac{[\ce{HO-}]}{\sqrt{K_{s1}}}\right) \\
&& = E°(\ce{Cu^{2+}}/\ce{Cu+}) + \num{0.06} \frac{1}{2} \log h
+ \num{0.06} \left(\frac{1}{2} \log \frac{K_e^2}{K_a K_{s1}} - \frac{1}{2}\log[\ce{Cl-}] \right) \\
&& = \SI{0.47}{V} - \num{0.03}\log c_{\text{tra}} - \num{0.03} \pH
\end{flalign*}
\end{subequations}
\end{document}
The first example (aligned within flalign) has correct numbering and spacing, but the chemical reactions (left side) and equations (right side) can not overlap, and that is not good when the reaction or equations are too long. The second example has correct width, but numbering is not that good (due to subequations being used), and the spacing between the reaction and the equations is too big.
Does anybody knows a way to have this kind of structure implemented in LaTeX?
