When calcium carbonate (CaCO_3) is heated strongly, which of the following occurs?

• A. It remains unchanged and does not react.
• B. It melts to form a liquid without any chemical change.
• C. It reacts with oxygen to form calcium peroxide (CaO_2).
• D. It decomposes to form calcium oxide (CaO) and carbon dioxide (CO_2).

Answer: (D)

Verified step by step guidance

1. Identify the type of reaction involved when calcium carbonate (CaCO_3) is heated strongly. This is typically a thermal decomposition reaction, where a compound breaks down into simpler substances upon heating.
2. Write the chemical formula for calcium carbonate: \(\text{CaCO}_3\).
3. Recall that upon strong heating, calcium carbonate decomposes into calcium oxide and carbon dioxide gas. The general form of the decomposition reaction is: \(\text{AB} \rightarrow \text{A} + \text{B}\), where AB is the original compound.
4. Write the balanced chemical equation for the decomposition of calcium carbonate: \(\text{CaCO}_3 (s) \xrightarrow{\Delta} \text{CaO} (s) + \text{CO}_2 (g)\), where \(\Delta\) indicates heating.
5. Understand that this reaction does not involve melting without chemical change, nor does it involve reaction with oxygen to form calcium peroxide. Instead, it is a decomposition producing calcium oxide and carbon dioxide gas.