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Science · 2025 · 3 marks
CBSE 2025 · Region 3 · Set 3 · Q27
State the change that is observed when a China dish containing copper powder is heated over the flame of a burner. Name the phenomenon responsible…
State the change that is observed when a China dish containing copper powder is heated over the flame of a burner. Name the phenomenon responsible for the change and write balanced equation for the chemical reaction that occurs. How is this reaction different from the reaction that occurs when copper wares kept in open air slowly lose their shiny brown surface and gain a coat ? Write chemical name of the coating and state its colour.
Marking-scheme solution
Reddish brown to black
Oxidation/Redox reaction
\(\displaystyle 2 \mathrm{Cu}+\mathrm{O}_{2} \xrightarrow{\text { Heat }} 2 \mathrm{CuO}\)
Corrosion occurs in open air whereas oxidation occurs on heating.
Basic copper carbonate / \(\displaystyle \mathrm{Cu}(\mathrm{OH})_{2} . \mathrm{CuCO}_{3}\)
Green
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