Question

Lime water turns milky when co2 is passed through it and further turns colourless when excess of co2 is bubbled through it. Explain

Answer 1

When CO2 is passed through lime-water, it turns milky due tothe formation of an insoluble precipitate of Calcium Carbonate.
The CaCO3 precipitate causes the milkiness. If you pass excess CO2 through lime-water, the CaCO3 reacts with the excess CO2 and waterto form calcium hydrogen carbonate or calcium bicarbonate.

Answer 2

So the solution turns milky.when we pass excess Co2 ,calcium bicarbonate Ca(HCO)3 formed which is soluble in water, So the solution turns transparent. When carbon dioxide is passed through lime water turns milky due to the formation of water insoluble precipitate CaCO3.