Which of the following is not decomposed by heat?

The compound that is not decomposed by heat is sodium carbonate (Na2CO3). When some compounds are heated, they break down into simpler substances. This process is called thermal decomposition. The products of thermal decomposition may include gases, liquids, or solids. Calcium carbonate (CaCO3), copper carbonate (CuCO3), zinc carbonate (ZnCO3), and magnesium carbonate (MgCO3) all decompose when heated to form simpler compounds. For example, when calcium carbonate is heated, it breaks down into calcium oxide (CaO) and carbon dioxide (CO2). However, sodium carbonate (Na2CO3) does not decompose when heated. It is a stable compound that can withstand high temperatures without breaking down. Therefore, it is used in many industrial processes that involve high temperatures, such as glass-making and soap-making. In summary, of the options given, sodium carbonate is the compound that is not decomposed by heat.