\textbf{222.} In the complete reaction of $49.10\,\mathrm{g}$ of a half-molar solution of phosphoric acid with sufficient calcium hydroxide solution, how many moles of substance are formed in water?
$$(\mathrm{H=1,\ O=16,\ P=31\,:\,g.mol^{-1}})$$
(1) $2.5\times10^{-2}$ \quad (2) $4.5\times10^{-2}$ \quad (3) $2.5\times10^{-3}$ \quad (4) $4.5\times10^{-3}$
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