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What Happens When CO2 Gas is Passed Through Lime Water and Why Does it Disappear on Passing Excess CO2

Answer: When CO2 is carried through lime water, calcium carbonate forms, which is insoluble in water and turns milky.

CaOH2Lime water+ CO2CaCO3Milkiness+ H2O 

When an excess of CO2 is passed through this solution, however, the milkiness goes away. This is due to the creation of colourless calcium bicarbonate, which is water soluble.

CaCO3Milkiness+ H2O + CO2CaHCO32water soluble