Question

Why lime water turn milky when carbon dioxide is passed through it?

Answer 1

Lime water turns milky when carbon dioxide is passed through it, due to the formation of insoluble calcium carbonate.

$$\begin{gathered} \mathrm{Ca}{\left(\mathrm{OH}\right)}_2+{\mathrm{CO}}_2\to {\mathrm{CaCO}}_3+{\mathrm{H}}_2\mathrm{O} \\ \left(\mathrm{Insoluble}\right) \end{gathered}$$