4

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

image

3

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

no align

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:

...
\[
\begin{aligned} 
    {\color{OliveGreen} 3} \\  {\color{OliveGreen} 1} 
\end{aligned}%
\begin{cases} % <------------- NOTE
    \ch{H2S -> S + 2 \el} \\
    \ch{Cr2O7\mch[2] + 6 \el -> 2 Cr\pch[3]}
\end{cases}
\]
...
  • 1
    Can you use cases? Or is it not suited for this case? – Moriambar Apr 14 '17 at 9:28
  • 1
    @Moriambar Yup I think so. It's embarrassing, I initially wanted to align the arrows, which is why I used aligned, but later I realised OP's pic is left aligned, so I just shifted the &s without thinking much. I'll add an addendum, thanks for the comment! – Troy Apr 14 '17 at 9:32
  • 1
    You shouldn't be embarassed: yours is a pretty good answer, I like it – Moriambar Apr 14 '17 at 9:33

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