Code: Select all
\documentclass{scrartcl}
\usepackage{chemmacros}
\newcommand{\ci}[1]{\tikz[baseline=(char.base)]{\node[shape=circle,draw,inner sep=1pt] (char) {#1};}}
\begin{document}
\begin{alignat*}{1}
(-1)\times \ci{1}& ~ \ce{H2O + KCl -> NH2 + CO2} \\
\ci{2}& ~ \ce{H2O -> CO3 + H3O+}
\end{alignat*}
\newreaction[arg,star]{reactionat}{alignat}
\begin{reactionat*}{1}
(-1)\times \ci{1}& ~ H2O + KCl -> NH2 + CO2 \\
\ci{2}& ~ H2O -> CO3 + H3O+
\end{reactionat*}
\end{document}