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.

(N/A) The gas that extinguishes a burning candle is carbon dioxide $(CO_2)$. Since the reaction produces $CO_2$ and calcium chloride $(CaCl_2)$ from a metal compound $A$ and hydrochloric acid $(HCl)$,the metal compound $A$ must be calcium carbonate $(CaCO_3)$.
The balanced chemical equation is:
$CaCO_{3(s)} + 2HCl_{(aq)} \rightarrow CaCl_{2(aq)} + CO_{2(g)} + H_2O_{(l)}$