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Science · 2023 · 3 marks
CBSE 2023 · Region 6 · Set 2 · Q31
A reddish brown metal used in electrical wires when powdered and heated strongly turns black. When hydrogen gas is passed over this black substance,…
A reddish brown metal used in electrical wires when powdered and heated strongly turns black. When hydrogen gas is passed over this black substance, it regains its original colour. Based on this information answer the following questions -
(a)
Name the metal and the black substance formed.
(b)
Write balanced chemical equations for the two reactions involved in the above information.
Marking-scheme solution
(a)
Cu / Copper
CuO / Copper Oxide
(b)
\(\displaystyle 2 \mathrm{Cu}+\mathrm{O}_{2} \xrightarrow{\text { Heat }} 2 \mathrm{CuO}\)
\(\displaystyle \mathrm{CuO}+\mathrm{H}_{2} \rightarrow \mathrm{Cu}+\mathrm{H}_{2} \mathrm{O}\)
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CBSE Class 10 Science past-paper question from the 2023 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.