\textbf{213-} A mixture of calcium carbonate and copper(II) sulfate pentahydrate contains \textbf{20\%} calcium by mass. What is the mass percent of water in the mixture?
$$(\mathrm{Cu=64,\ Ca=40,\ S=32,\ O=16,\ C=12,\ H=1:\ g.mol^{-1}})$$
\begin{itemize}
\item[(1)] $9$ \hfill (2) $18$
\item[(3)] $13/5$ \hfill (4) $22/5$
\end{itemize}
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