On passing excess carbon dioxide gas through lime water, it first turns milky and then becomes colourless, explain why ? Write all the chemical equation related to it.

Explanation

On passing carbon dioxide through lime water, initially a precipitate of calcium carbonate is formed and on passing excess of carbon cioxide the calcium carbonate is reduced to calcium bicarbonate, which is soluble in aqueous medium , hence the solution becomes colourless.
`Ca(OH)_(2)(aq.)+CO_(2)(g)toCaCO_(3)(s)+H_(2)O(l)`
`CaCO_(3)(s)+CO_(2)(g)+H_(2)O(l) toCa(HCO_(3))_(2)(aq.)`.