Question

On passing excess co2 gas through lime water,it first turns milky andvthen becomes colourless .why?

Answer 1

The first reaction produces CaCO3 which is insoluble in water and hence the solution turns milky.If furthermore CO2 is passed,the CaCO3 reacts with the CO2 to form Ca(HCO3)2 which is soluble in water and hence the solution becomes colourless.Ca(OH)2 [lime water] + CO2 — CaCO3 + H2OCaCO3 + CO2 + H2O — Ca(HCO3)2