Is ZnCO3(s) → ZnO(s) + CO2(g) a redox reaction?

• A. Yes
• B. No
• C. Only oxidation
• D. Only reduction

Answer: (B)

Oxidation-state changes determine whether a reaction is redox. In ZnCO3, zinc is +2, carbon in the carbonate is +4, and oxygen is -2. In the products ZnO and CO2, zinc remains +2, carbon remains +4, and oxygen remains -2. No oxidation state changes occur for any element, so no electron transfer happens. Redox reactions require at least one species to be oxidized and another to be reduced, which this reaction does not show. Therefore, this decomposition is not a redox reaction; it’s a thermal decomposition that rearranges atoms and releases CO2 without electron transfer.