chemfig - Redox semi-reaction

Question

It is possible write the two redox half-reactions inside a brace, so as to obtain a thing as in this figure? I'm using chemfig package

Answer 1

Here's my small attempt at creating the half equations.

The code:

\documentclass{article}
\usepackage{amsmath}
\usepackage[dvipsnames]{xcolor}
\usepackage{chemmacros}
\begin{document}
    \[
    \begin{aligned} 
        {\color{OliveGreen} 3} \\  {\color{OliveGreen} 1} 
    \end{aligned}%
    \left\{%
        \begin{aligned} 
        &\ch{H2S -> S + 2 \el} \\
        &\ch{Cr2O7\mch[2] + 6 \el -> 2 Cr\pch[3]}
        \end{aligned}
    \right.
    \]
    \centerline{\rule{6cm}{1pt}}
    \[
    {\color{OliveGreen} 8 \color{blue} \ch{H\pch}} + 
    {\color{OliveGreen} 3} \ch{H2S + Cr2O7\mch[2] ->}
    {\color{OliveGreen} 3} \ch{S + 2 Cr\pch[3] +}
    {\color{OliveGreen} 7 \color{blue} \ch{H2O}}
    \]
\end{document}

Addendum

If alignment is not a huge issue for the half equations, then \begin{cases}...\end{cases} is a more succinct answer (Thanks @Moriambar!). In that case (no pun intended), the half equations can be typeset as such:

...
\[
\begin{aligned} 
    {\color{OliveGreen} 3} \\  {\color{OliveGreen} 1} 
\end{aligned}%
\begin{cases} % <------------- NOTE
    \ch{H2S -> S + 2 \el} \\
    \ch{Cr2O7\mch[2] + 6 \el -> 2 Cr\pch[3]}
\end{cases}
\]
...