Question

When the gas formed on heating limestone is passed through freshly prepared lime water, the lime water turns milky.

Answer 1

(i) On heating, limestone undergoes thermal decomposition to form calcium oxide (quick lime) and carbon dioxide.
`CaCO_(3(s))overset(Delta)tounderset("quick lime")(CaO_((s)))+CO_(2)uarr`
(ii) Calcium oxide when dissolved in water forms Calcium hydroxide (lime water).
`CaO_((s))+H_(2)O_((l))to underset("Calcium hydroxide")(Ca(OH)_(2(aq)))`
(iii) When carbon dioxide is passed through lime water it turns milky due to formation of white precipitate of Calcium carbonate.
`Ca(OH)_(2(aq))+CO_(2(g))to underset("Calcium carbonate")(CaCO_(3(s)))+H_(2) O_((l))`