When heated, metallic carbonates generally produce — Stoichiometry Chemistry Question

STEPS:

1. Identify the Reaction Type: The question describes a process where a substance is "heated" to produce other substances, which is the definition of thermal decomposition.
2. Analyze the Reactant: The starting material is a metallic carbonate, which consists of a metal cation and the carbonate polyatomic ion ($CO_3^{2-}$). The general formula can be represented as $MCO_3$.
3. Apply the General Rule for Carbonates: In chemistry, a fundamental rule is that most metal carbonates (with the exception of some Group 1 metals like sodium or potassium, which are extremely heat-stable) decompose when heated to produce a metallic oxide and carbon dioxide gas ($CO_2$).
4. Formulate a Representative Equation: Consider a common example like calcium carbonate: $CaCO_3(s) \xrightarrow{\Delta} CaO(s) + CO_2(g)$. This balanced equation demonstrates that the products are a metallic oxide ($CaO$) and $CO_2$.
5. Conclusion: The products of heating a metallic carbonate are a metallic oxide and $CO_2$, which matches option E.

WHY_OTHERS_WRONG:

• A) metallic peroxide + CO: Metallic peroxides are typically formed by reacting certain metals with excess oxygen, not by decomposing carbonates. Additionally, $CO$ production would imply a reduction of the carbon atom, which does not occur in this decomposition.
• B) metal + CO + $O_2$: Decomposing a carbonate into a pure metal would require a significant redox reaction that simple heating does not provide for most metal carbonates.
• C) metallic hydroxide + $CO_2$: A hydroxide ($OH^-$) contains hydrogen, which is not present in the chemical formula of a pure metallic carbonate ($MCO_3$). Therefore, it is impossible to form a hydroxide as a product.
• D) metallic oxalate + $O_2$: Oxalates ($C_2O_4^{2-}$) are more complex than carbonates and are generally less stable; they would decompose *into* carbonates or oxides rather than being produced by them.