Which statement is true for the following chemical reactions?

CuCO3+ heat → CuO + CO2

CuO + SnO → Cu + SnO2

CO2 is oxidised and SnO2 is reduced

CuCO3 is oxidised and CuO is reduced

CuO is oxidised and SnO is reduced

SnO is oxidised and CuO is reduced

The correct statement is SnO is oxidised and CuO is reduced. This applies to the second reaction, CuO + SnO → Cu + SnO₂, where SnO loses electrons (oxidized from +2 to +4 in SnO₂) and CuO gains electrons (Cu reduced from +2 to 0 in Cu).

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Reaction Breakdown

The first reaction, CuCO₃ + heat → CuO + CO₂, is thermal decomposition, not a redox process since copper stays at +2 oxidation state throughout. No species undergoes oxidation or reduction here, making options referencing this incorrect for redox identification.

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Option Explanations

• CO₂ is oxidised and SnO₂ is reduced: False. CO₂ forms in the first non-redox reaction and stays at +4 for carbon; SnO₂ is the product (oxidized form), not reduced.

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• CuCO₃ is oxidised and CuO is reduced: False. Neither changes oxidation state in decomposition; Cu remains +2 in both.

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• CuO is oxidised and SnO is reduced: False. CuO acts as oxidant (reduced), while SnO is oxidized.

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• SnO is oxidised and CuO is reduced: True. In the second reaction, Sn oxidation state rises from +2 to +4, and Cu drops from +2 to 0, confirming redox roles.

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