\documentclass{webquiz}
\usepackage[version=4]{mhchem}
\Department{Chemistry}
\UnitCode{Chem101}\UnitURL{/chem101}
\title{Display as image example}
\begin{document}
  \DisplayAsImage[style="vertical-align: middle;"]{ce}
  \begin{question}
    What is \ce{(NH4)2S}?
    \begin{choice}[columns=1]
      \correct Ammonium sulfide
      \incorrect Ammonium hydrosulfide
      \feedback This is \ce{(NH4)HS}
    \end{choice}
  \end{question}
\end{document}
