How to make the arrow in a chemical formula shorter? (using mhchem)

\documentclass{article}
\usepackage[version=4]{mhchem}

\ExplSyntaxOn
\keys_define:nn { mhchem }
 {
  arrow-min-length .code:n =
   \cs_set:Npn \__mhchem_arrow_options_minLength:n { {#1} } % default is 2em
 }
\ExplSyntaxOff

\begin{document}

\ce{(2Na+,SO4^2- ) + (Ba^2+, 2Cl- ) -> BaSO4 v + 2NaCl}

\mhchemoptions{arrow-min-length=1em}

\ce{(2Na+,SO4^2- ) + (Ba^2+, 2Cl- ) -> BaSO4 v + 2NaCl}

\mhchemoptions{arrow-min-length=10em}

\ce{(2Na+,SO4^2- ) + (Ba^2+, 2Cl- ) -> BaSO4 v + 2NaCl}

\end{document}