JEE Advance - Chemistry (2023 - Paper 1 Online - No. 1)
The correct statement(s) related to processes involved in the extraction of metals is(are) :
Roasting of Malachite produces Cuprite.
Calcination of Calamine produces Zincite.
Copper pyrites is heated with silica in a reverberatory furnace to remove iron.
Impure silver is treated with aqueous $\mathrm{KCN}$ in the presence of oxygen followed by reduction with zinc metal.
Explanation
(A) Roasting of malachite
$$ \mathrm{CuCO}_3 \mathrm{Cu}(\mathrm{OH})_2 \underset{+\mathrm{O}_2}{\stackrel{\Delta}{\longrightarrow}} \mathrm{CuO}+\mathrm{H}_2 \mathrm{O}+\mathrm{CO}_2 $$
Roasting means that heating of substance in excess of oxygen. So cuprite $\mathrm{Cu}_2 \mathrm{O}$ is not produced. Hence, this statement is not correct.
(B) Calcination means heating in absence of air
$$ \underset{\text { Calamine }}{\mathrm{ZnCO}_3} \stackrel{\Delta}{\longrightarrow} \underset{\text { Zincite }}{\mathrm{ZnO}}+\mathrm{CO}_2 $$
$\therefore$ Statement is true.
(C)
$$ \begin{aligned} \mathrm{CuFeS}_2+\mathrm{O}_2 \stackrel{\Delta}{\longrightarrow} \mathrm{Cu}_2 \mathrm{~S}+\mathrm{FeO}+\mathrm{SO}_2 \\\\ \mathrm{FeO}+\mathrm{SiO}_2 \longrightarrow \mathrm{FeSiO}_2 \end{aligned} $$
$\therefore$ Statement is true.
(D)
$$ \begin{aligned} \mathrm{Ag}+\mathrm{KCN}+\mathrm{O}_2+2 \mathrm{H}_2 \mathrm{O} \longrightarrow & 4 \mathrm{~K}\left[\mathrm{Ag}(\mathrm{CN})_2\right] +4 \mathrm{KOH} \\\\ 2 \mathrm{~K}\left[\mathrm{Ag}(\mathrm{CN})_2\right]+\mathrm{Zn} \longrightarrow & \mathrm{K}_2\left[\mathrm{Zn}(\mathrm{N})_4\right]+2 \mathrm{Ag} \end{aligned} $$
Silver is obtained by reaction with Zinc
So, the above statement is true.
$$ \mathrm{CuCO}_3 \mathrm{Cu}(\mathrm{OH})_2 \underset{+\mathrm{O}_2}{\stackrel{\Delta}{\longrightarrow}} \mathrm{CuO}+\mathrm{H}_2 \mathrm{O}+\mathrm{CO}_2 $$
Roasting means that heating of substance in excess of oxygen. So cuprite $\mathrm{Cu}_2 \mathrm{O}$ is not produced. Hence, this statement is not correct.
(B) Calcination means heating in absence of air
$$ \underset{\text { Calamine }}{\mathrm{ZnCO}_3} \stackrel{\Delta}{\longrightarrow} \underset{\text { Zincite }}{\mathrm{ZnO}}+\mathrm{CO}_2 $$
$\therefore$ Statement is true.
(C)
$$ \begin{aligned} \mathrm{CuFeS}_2+\mathrm{O}_2 \stackrel{\Delta}{\longrightarrow} \mathrm{Cu}_2 \mathrm{~S}+\mathrm{FeO}+\mathrm{SO}_2 \\\\ \mathrm{FeO}+\mathrm{SiO}_2 \longrightarrow \mathrm{FeSiO}_2 \end{aligned} $$
$\therefore$ Statement is true.
(D)
$$ \begin{aligned} \mathrm{Ag}+\mathrm{KCN}+\mathrm{O}_2+2 \mathrm{H}_2 \mathrm{O} \longrightarrow & 4 \mathrm{~K}\left[\mathrm{Ag}(\mathrm{CN})_2\right] +4 \mathrm{KOH} \\\\ 2 \mathrm{~K}\left[\mathrm{Ag}(\mathrm{CN})_2\right]+\mathrm{Zn} \longrightarrow & \mathrm{K}_2\left[\mathrm{Zn}(\mathrm{N})_4\right]+2 \mathrm{Ag} \end{aligned} $$
Silver is obtained by reaction with Zinc
So, the above statement is true.
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