CBSE 2025 · Region 3 · Set 3 · Q27 · 3 marks
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
Chemical Reactions and EquationsOxidation and ReductionApplyshort_answermedium
More from Chemical Reactions and Equations
- Why do we balance a chemical equation? Name and state the law that suggests the balancing of a chemical…2025 · asked 3×
- The main observations while performing the experiment of burning magnesium ribbon in air are: (i) Magnesium…2025 · asked 3×
- In which one of the following situations a chemical reaction does not occur?2025 · asked 3×
- The colour of the solution observed after about 1 hour of placing iron nails in copper sulphate solution is2025 · asked 3×
- Assertion: Silver chloride turns grey in sunlight. Reason (R): Decomposition of silver chloride into silver…2025 · asked 3×
- Assertion: Decomposition reactions are generally endothermic reactions. Reason (R): Decomposition of organic…2025 · asked 3×
- List the possible sources of energy required in decomposition reactions. Illustrate any one with a suitable…2025 · asked 3×
- Electrolysis of water is a decomposition reaction. The mass ratio (M H: M O) of hydrogen and oxygen gases…2025 · asked 3×
CBSE Class 10 Science past-paper question from the 2025board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.