A student dropped a few pieces of marble chips in dilute hydrochloric acid contained in a test tube. The gas evolved was passed through lime water. What changes would be observed lime water ? Write the chemical equations for both the changes observed.

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.)`.