\textbf{213.} A solution of 23\% by mass ethanol in water, approximately how many moles per liter is it?\\
$(d_{\text{solution}} = 0.9\,\text{g.mL}^{-1};\; O=16,\, C=12,\, H=1:\text{g.mol}^{-1})$
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(1) $3.5$ \hfill (2) $4.5$ \hfill (3) $3$ \hfill (4) $4$
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