What is ionic reaction equation for reaction between carbon dioxide and limewater?


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> Write the ionic reaction equation for the reaction
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> \[\ce{Ca(OH)2(aq) + CO2(g) <=> CaCO3(s) + H2O(l)}.\]
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I first wrote the complete ionic equation as such:
\[\ce{Ca^2+ + 2 OH^- + CO2 <=> Ca^2+ + CO3^2- + H2O}.\tag{R1}\]
Then I crossed out the common $\ce{Ca^2+}$, and got
\[\ce{2OH^- + CO2 <=> CO3^2- + H2O}.\tag{R2}\]
How is this wrong?




$\ce{CaCO3}$ is a precipitate. It is not made of separated $\ce{Ca^{2+}}$ and $\ce{CO3^{2-}}$ ions. So the equation is : $$\ce{Ca^{2+} + 2 OH^- + CO2 -> CaCO3 + H2O}$$ This equation may be considered as two successive equations, namely :$$\ce{CO2 + 2 OH^- -> CO3^{2-} + H2O}$$ and $$\ce{Ca^{2+} + CO3^{2-} -> CaCO3}$$


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