Which of the following describes the chemical property of acids?

Analysis of the Question

The question asks for the general chemical property of acids when they react with carbonates. In chemistry, acids undergo specific neutralization and displacement reactions. We need to identify the correct balanced chemical equation that represents the reaction between an acid and a metal carbonate.

Concept Explanation

When an acid reacts with a metal carbonate (represented here as $X_nCO_3$, where $X$ is a metal), the reaction follows a standard pattern: Acid + Metal Carbonate $\to$ Salt + Water + Carbon(IV) oxide

• Acid: Provides the hydrogen ions ($H^+$).
• Metal Carbonate: Provides the carbonate ion ($CO_3^{2-}$).
• Products: The metal from the carbonate combines with the anion of the acid to form a salt. The hydrogen from the acid combines with the oxygen from the carbonate to form water ($H_2O$), and the remaining carbon and oxygen form carbon(IV) oxide ($CO_2$).

Step-by-Step Solution

Let’s evaluate the options provided:

• Option B: $Acid + XCO_3 \to Salt + H_2O + NH_3$. This is incorrect because the reaction between an acid and a carbonate produces $CO_2$, not ammonia ($NH_3$).
• Option C: $Acid + NaOH \to Normal salt + CO_2$. This is incorrect because $NaOH$ is a base (alkali), not a carbonate. The reaction between an acid and a base (neutralization) produces only salt and water ($Acid + Base \to Salt + Water$).
• Option D: $Acid + X_nCO_3 \to Salt + H_2O + CO_2$. This perfectly matches the general chemical principle described above. The "$n$" in $X_nCO_3$ represents the valency of the metal $X$, which is standard notation for chemical formulas.

Conclusion

The reaction between an acid and a metal carbonate consistently yields a salt, water, and carbon(IV) oxide. Option D is the only equation that correctly represents these products.

Exam Tip: Whenever you see a reaction involving a carbonate ($CO_3$) and an acid, always look for $CO_2$ in the products. If you see $NH_3$ or other gases, you can immediately rule those options out!