International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

Which of the following accurately describes the end products of the thermal decomposition of calcium carbonate?

1. Calcium and Carbon monoxide

2. Calcium oxide and Carbon dioxide

3. Calcium hydroxide and Oxygen

4. Calcium and Carbon

The correct answer is: Calcium oxide and Carbon dioxide

The accurate description of the end products of the thermal decomposition of calcium carbonate involves understanding the chemical process it undergoes when heated. When calcium carbonate (CaCO₃) is subjected to high temperatures, it thermally decomposes into calcium oxide (CaO) and carbon dioxide (CO₂). This reaction can be represented by the equation: \[ \text{CaCO}_3 \rightarrow \text{CaO} + \text{CO}_2 \uparrow \] During the decomposition, calcium oxide, also known as quicklime, and carbon dioxide gas are formed. The process is significant in various industries, such as in the production of lime and in carbon capture technologies. The other options do not accurately represent the products formed during this decomposition. For instance, calcium and carbon monoxide, calcium hydroxide and oxygen, as well as calcium and carbon, do not correlate with the actual decomposition of calcium carbonate under thermal conditions. This clear transformation highlights why calcium oxide and carbon dioxide are indeed the correct products of this reaction.