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.
The gas evolved is carbon dioxide which extinguishes a burning candle. Since one of the compounds formed is calcium chloride, the metal compound A must be calcium carbonate (CaCO₃).
The balanced chemical equation for the reaction is:
CaCO₃(s) + 2HCl(aq) → CaCl₂(aq) + H₂O(l) + CO₂(g)
This reaction follows the general pattern where metal carbonates react with acids to give a corresponding salt, carbon dioxide and water. The effervescence is due to the evolution of carbon dioxide gas.
Explanation
The question tests understanding of how metal carbonates react with acids. From the context, all metal carbonates and hydrogencarbonates react with acids to give a corresponding salt, carbon dioxide and water. Since calcium chloride is formed, the metal compound must contain calcium - hence calcium carbonate (CaCO₃). The gas that extinguishes a burning candle is carbon dioxide, as mentioned in the fire extinguisher section of the context.
Solution Steps
Step 1: Identify that the gas which extinguishes a burning candle is carbon dioxide (CO₂)
Step 2: Since calcium chloride (CaCl₂) is formed and the acid is HCl, the metal compound must be calcium carbonate (CaCO₃)
Step 3: Write the reaction: Metal carbonate + Acid → Salt + Water + Carbon dioxide
Step 4: Balance the equation: CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂