Metal compound A reacts with dilute hydrochloric acid to produce effervescence. The gas evolved extinguishes a burning candle. Write a balanced chemical equation for the reaction if one of the compounds formed is calcium chloride.

Explanation

The gas that extinguishes a burning candle is carbon dioxide which is formed by the action of dilute hydrochloric acid on a metal carbonate (or metal hydrogencarbonate) and produces effervescence. Now, since one of the compounds formed is calcium chloride, it shows that the metal compound is calcium carbonate (it cannot be calcium hydrogencarbonate because calcium hydrogencarbotae is found only in solution, it is too unstable to exist as a solid). thus, the metal compound A is alcium carbonate `(CaCO_(3))`. Calcium carbonate reacts with dilute hydrochloric acid to form calcium chloride, carbon dioxide and water.
This can be written as:
`underset("Calcium carbonate")(CaCO_(3))(s)-underset("Hydrochloric acid")(2HCl(aq))tounderset("Calcium chloride")(CaCl_(2)(aq))+underset("Carbon dioxide")(CO_(2)(g))+underset("water")(H_(2)O(l))`