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Science · 2023 · 3 marks
CBSE 2023 · Region 2 · Set 3 · Q28
(a)Copper reacts with a moist gas 'A' in the air and slowly loses its shiny brown surface. It turns green. Identify 'A' and the substance of the green coating formed on the surface of copper.(b)How is copper obtained from its sulphide ore ? Write the chemical equations for the reaction involved in its extraction.
(a)
Copper reacts with a moist gas 'A' in the air and slowly loses its shiny brown surface. It turns green. Identify 'A' and the substance of the green coating formed on the surface of copper.
(b)
How is copper obtained from its sulphide ore ? Write the chemical equations for the reaction involved in its extraction.
Marking-scheme solution
(a) Gas 'A' - \(\displaystyle \mathrm{CO}_{2}\) / Carbon dioxide
Green substance - Basic copper carbonate. / \(\displaystyle \left[\mathrm{CuCO}_{3} . \mathrm{Cu}(\mathrm{OH})_{2}\right]\)
(b) Roasting
\[2 \mathrm{Cu}_{2} \mathrm{~S}+3 \mathrm{O}_{2} \xrightarrow{\Delta} 2 \mathrm{Cu}_{2} \mathrm{O}+2 \mathrm{SO}_{2}
\]
\[2 \mathrm{Cu}_{2} \mathrm{O}+\mathrm{Cu}_{2} \mathrm{~S} \longrightarrow 6 \mathrm{Cu}+\mathrm{SO}_{2}
\]
CBSE Class 10 Science past-paper question from the 2023board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.