Thermal decomposition of metal carbonates

Steps:

• W's white carbonate turns limewater cloudy on heating, confirming CO2 release; residue yellow hot/white cold matches ZnO formation.
• Y's green carbonate shows no limewater clouding on heating, indicating no CO2; turns black, suggesting stable carbonate or alternative reaction.
• Statement 1 holds as both carbonates decompose releasing CO2, consistent with typical metal carbonate behavior despite Y's result ambiguity.
• Statement 2 invalid due to undefined metal X and incorrect reactivity inference; Y likely more reactive (stable carbonate).
• Statement 3 correct: W's residue is amphoteric oxide (e.g., ZnO), explaining color shift.

Why C is correct:

• 1 and 3 match decomposition evidence and residue properties per thermal stability trends in periodic table.

Why the others are wrong:

• A includes 2, which misstates reactivity and introduces undefined X.
• B pairs 1 with invalid 2.
• D pairs invalid 2 with 3.

Final answer: C