\textbf{233 - In how many of the following compounds is the ratio of the number of anions to cations equal to the sulfide ion in Chromium(III) sulfide?}
\begin{itemize}
\item Calcium phosphate \hfill Scandium oxide \hfill Aluminum sulfate
\item Gallium carbonate \hfill Silicon dioxide \hfill Iron(III) nitrate
\end{itemize}
\begin{center}
(1) 2 \qquad (2) 3 \qquad (3) 4 \qquad (4) 5
\end{center}
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